Porous medium with adjustable fluid permeability and associated systems and methods

ABSTRACT

The present disclosure is related to porous media with adjustable fluid permeabilities and related systems and methods. In certain cases, the fluid permeability of a porous medium can be adjusted by applying an electrical potential to the porous medium. In some such cases, the application of the electrical potential to the porous medium results in the deposition of material over or the removal of material from the porous medium. Also disclosed herein are systems and methods for capturing species (e.g., acid gases) in which porous media with adjustable fluid permeabilities are used, for example, to control the flow of fluid into and out of a medium used to capture the species.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application No. 63/002,490, filed Mar. 31, 2020, andentitled “Porous Medium with Adjustable Fluid Permeability andAssociated Systems and Methods,” which is incorporated herein byreference in its entirety for all purposes.

TECHNICAL FIELD

Porous media having adjustable fluid permeabilities, and associatedsystems and methods, are generally described.

SUMMARY

The present disclosure is related to porous media with adjustable fluidpermeabilities and related systems and methods. In certain cases, thefluid permeability of a porous medium can be adjusted by applying anelectrical potential to the porous medium. In some such cases, theapplication of the electrical potential to the porous medium results inthe deposition of material over or the removal of material from theporous medium. Also disclosed herein are systems and methods forcapturing species (e.g., acid gases) in which porous media withadjustable fluid permeabilities are used, for example, to control theflow of fluid into and out of a medium used to capture the species. Thesubject matter of the present invention involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In certain aspects, a method is provided.

In some embodiments, the method comprises transporting a fluid through afirst electronically conductive porous solid such that a species fromthe fluid is captured by a medium adjacent to the first electronicallyconductive porous solid; altering an electrical potential appliedbetween the first electronically conductive porous solid and a secondelectronically conductive porous solid such that the fluid permeabilityof the first electronically conductive porous solid is reduced and thefluid permeability of the second electronically conductive porous solidis increased; and releasing the species from the medium such that thespecies is transported through the second electronically conductiveporous solid.

In certain embodiments, the method comprises applying an electricalpotential to an electronically conductive porous solid to adjust a fluidpermeability of the electronically conductive porous solid.

In some aspects, a device is provided.

In certain embodiments, the device comprises a first electronicallyconductive porous solid; a second electronically conductive porous solidelectronically coupled to the first electronically conductive poroussolid; and a medium between the first electronically conductive poroussolid and the second electronically conductive porous solid; wherein thedevice is configured such that: when an electrical potential is appliedto the first and second electronically conductive porous solids with afirst polarity, a fluid permeability of the first electronicallyconductive porous solid is reduced, and when an electrical potential isapplied to the first and second electronically conductive porous solidswith a second polarity opposite the first polarity, the fluidpermeability of the second electronically conductive porous solid isreduced.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale unless otherwiseindicated. In the figures, each identical or nearly identical componentillustrated is typically represented by a single numeral. For purposesof clarity, not every component is labeled in every figure, nor is everycomponent of each embodiment of the invention shown where illustrationis not necessary to allow those of ordinary skill in the art tounderstand the invention.

FIGS. 1A-1C are cross-sectional schematic illustrations showing theadjustment of the fluid permeability of a porous medium, according tocertain embodiments;

FIG. 1D is a perspective view schematic illustration of a porous medium,according to certain embodiments;

FIGS. 2A-2C are cross-sectional schematic illustrations showing theadjustment of fluid permeabilities of two porous media between which amedium for the capture of species is located, according to certainembodiments;

FIGS. 3A-3C are cross-sectional schematic illustrations showing theadjustment of fluid permeabilities of two porous media between which amedium for the electrochemical capture of species is located, accordingto certain embodiments;

FIGS. 4A-4C are cross-sectional schematic illustrations showing thetortuosities of pores of a porous medium, according to certainembodiments;

FIG. 5A is a perspective view schematic illustration of a porous mediumin an open state, according to certain embodiments;

FIG. 5B is a perspective view schematic illustration of a porous mediumin a closed state, according to certain embodiments;

FIG. 5C is, according to certain embodiments, a cross-sectionalschematic illustration of a system comprising multiple porous media, inwhich the left-hand side medium is permeable to a gaseous stream and theright-hand side medium is not permeable to a gaseous stream;

FIG. 5D is, according to certain embodiments, a cross-sectionalschematic illustration of a system comprising multiple porous media, inwhich the left-hand side medium is not permeable to a gaseous stream andthe right-hand side medium is permeable to a gaseous stream;

FIG. 6A is, according to some embodiments, a scanning electronmicroscope (SEM) image of a pristine anodic aluminum oxide (AAO)membrane;

FIG. 6B is, according to certain embodiments, an SEM image of anAu-coated AAO membrane;

FIG. 6C is, according to some embodiments, a photo image of a pristineanodic aluminum oxide (AAO) membrane;

FIG. 6D is, according to certain embodiments, a photo image of anAu-coated AAO membrane;

FIG. 6E is a plot, according to some embodiments, of current as afunction of voltage;

FIG. 6F is, according to some embodiments, a plot of potential as afunction of time;

FIG. 6G is, according to certain embodiments, a top view image of Zndeposited on an AAO membrane;

FIG. 6H is, according to some embodiments, a top view image of Zndeposited on an AAO membrane;

FIG. 6I is, according to certain embodiments, a side view image of Zndeposited on an AAO membrane;

FIG. 7A is, according to certain embodiments, a set of photo imagesshowing liquid-state diffusion tests at different time points forpristine AAO and 0.5 mAh cm⁻² Zn gated AAO;

FIG. 7B shows, according to some embodiments, cross-over dyeconcentration in a permeate chamber as a function of time for pristineAAO, and AAO gated with 0.1, 0.3, and 0.5 mAh cm⁻² Zn;

FIG. 7C is, according to certain embodiments, a schematic illustrating asetup for ex situ gas-phase testing of an electrochemically-mediatedgating membrane;

FIG. 7D is, according to some embodiments, a plot showing CO₂concentrations in an N₂ sweep stream under different gas flowconditions;

FIG. 8A is, according to certain embodiments, a schematic illustrating asetup for in situ testing of an electrochemically-mediated gas gatingmembrane;

FIG. 8B is, according to certain embodiments, a plot of CO₂ permeationas a function of time showing permeated CO₂ concentration in response toreversible gating;

FIG. 8C is, according to some embodiments, a plot of CO₂ permeation as afunction of time showing the detailed gating response of one singledeposition/dissolution cycle marked with the dashed line in FIG. 8B;

FIG. 8D is, according to certain embodiments, a plot of coulombicefficiency as a function of cycle number;

FIG. 8E is, according to some embodiments, a plot of CO₂ permeation as afunction of time, showing gating responses under different Zn cyclingcurrent densities;

FIG. 9A is, according to certain embodiments, a plot showing CO₂capture-release voltage profiles of electrodes with different areal massloadings and cycling rates;

FIG. 9B is, according to certain embodiments, a plot showing the cyclingstability of certain electrodes;

FIG. 9C is, according to some embodiments, a schematic illustrating adiffusion model for a limiting current density calculation;

FIG. 9D is, according to certain embodiments, a plot of steady-state CO₂concentration as a function of current density;

FIG. 9E is, according to certain embodiments, a plot showing CO₂permeation in response to electrochemical cycling of the CO₂ cell, andthe corresponding voltage profiles;

FIG. 9F is, according to some embodiments, a plot of CO₂ permeation as afunction of time;

FIG. 10A is, according to certain embodiments, a cross-sectionalschematic of an integrated CO₂ separation system;

FIG. 10B is, according to some embodiments, a set of schematicillustrations showing “closed” and “open” configurations;

FIG. 10C is, according to certain embodiments, a set of plots showingCO₂ permeation during operation of an integrated CO₂ separation system,and the corresponding voltage profiles of the CO₂ cell and the gatingcell;

FIG. 10D is, according to certain embodiments, a plot of CO₂ permeationas a function of time;

FIG. 11A is, according to some embodiments, an SEM image of an Au-coatedAAO membrane;

FIG. 11B is, according to certain embodiments, an energy-dispersiveX-ray elemental mapping of the Au-coated AAO membrane shown in FIG. 11A;

FIG. 12A is, according to some embodiments, a diagram showing standardreduction potentials of common metallic redox pairs;

FIG. 12B is, according to certain embodiments, a plot of current as afunction of potential for 1.0 M Zn(NO₃)₂ in dimethyl sulfoxide, 1.0 MNi(NO₃)₂ in dimethyl sulfoxide, and 5 mM anthraquinone in dimethylsulfoxide with 0.1 M tetrabutylammonium hexafluorophosphate supportingsalt under CO₂ atmosphere;

FIGS. 13A-13C are, according to certain embodiments, SEM images of Zndeposition morphology on an Au-coated aluminum foil;

FIG. 14 is, according to certain embodiments, a photo image showing apristine copper foil (left) and the copper foil after Zn depositionusing aqueous electrolyte (right);

FIGS. 15A-15B are, according to some embodiments, low-magnification SEMimages of Zn deposition on an Au-coated AAO membrane;

FIG. 16A is, according to some embodiments, an SEM image of Zn depositedon Au-coated AAO membrane;

FIGS. 16B-16E are, according to certain embodiments, energy-dispersiveX-ray elemental mappings of the Zn deposited Au-coated AAO membraneshown in FIG. 16A;

FIG. 17A is, according to certain embodiments, a plot showing Zndeposition/dissolution voltage profiles at different current densitiesand the corresponding CE;

FIG. 17B is, according to certain embodiments, a plot showing a voltageprofile of Zn deposition/dissolution at a current density of 12 mA cm⁻²,followed by a low-current dissolution step;

FIGS. 18A-18C are, according to some embodiments, photo images of Zndeposited on AAO membranes at different deposition capacities;

FIGS. 18D-18F are, according to certain embodiments, SEM images of theZn deposited on AAO membranes from FIGS. 18A-18C;

FIG. 19A is, according to certain embodiments, a plot of UV-Vis spectraof aqueous solutions of methyl orange at different concentrations;

FIG. 19B is, according to some embodiments, a concentration calibrationcurve based on absorbance at 464 nm;

FIG. 20 is, according to certain embodiments, a set of photo imagesshowing liquid-state diffusion tests at different time points;

FIG. 21A is, according to some embodiments, a schematic showing theconfiguration of a gas cell device;

FIG. 21B is, according to certain embodiments, a schematic showing thedimensions of the gas flow chamber of the device shown in FIG. 21A;

FIG. 21C is, according to certain embodiments, an image of the gas celldevice shown in FIG. 21A;

FIG. 22A is, according to some embodiments, a plot of CO₂ permeation asa function of Zn deposition capacity during ex situ gas phase testingwhen a 15% CO₂ feed stream and an N₂ sweep stream were under the sameflow rates;

FIG. 22B is, according to certain embodiments, a plot of CO₂ permeationas a function of Zn deposition capacity during ex situ gas phase testingwhen a 15% CO₂ feed stream and an N₂ sweep stream were under differentflow rates;

FIG. 23 is, according to some embodiments, a photo image showing a Zndeposited stainless-steel mesh counter electrode used for in situtesting of an electrochemically-mediated gas gating membrane;

FIG. 24A is, according to certain embodiments, a plot of steady-stateCO₂ cross-over concentration using a 10 sccm 100% CO₂ feed stream and a2 sccm N₂ sweep stream;

FIG. 24B is, according to certain embodiments, a plot of CO₂ permeationas a function of time showing a characterization on the detectorresponse time;

FIG. 25 is, according to some embodiments, a plot of voltage as afunction of capacity showing a Zn deposition/dissolution voltage profileat a 1st, 10^(th), and 20^(th) cycle during in situ gas cell testing;

FIG. 26A is, according to certain embodiments, a schematic showing theconfiguration of an integrated CO₂ gas separation system;

FIG. 26B is, according to some embodiments, a photo image of a gatingmembrane mounted on a brass gasket using epoxy glue;

FIG. 26C is, according to certain embodiments, a photo image of an LFPelectrode;

FIG. 26D is, according to some embodiments, a photo image of a PAQelectrode;

FIG. 26E is, according to certain embodiments, a photo image of a rubbergasket used to confine a CO₂ cell within a gating cell;

FIG. 27A is, according to certain embodiments, a plot of potential as afunction of capacity showing a typical voltage profile of a gating cellin an integrated CO₂ separation system;

FIG. 27B is, according to some embodiments, a plot of potential as afunction of capacity showing a typical voltage profile of a CO₂ cell inan integrated CO₂ separation system; and

FIG. 27C is, according to certain embodiments, a plot of CO₂ permeationas a function of time showing a continuous capture-release cycling of anintegrated CO₂ separation system with 100% CO₂ as the feed stream.

DETAILED DESCRIPTION

Porous media with adjustable fluid permeabilities, and related systemsand methods, are generally described. Certain embodiments are related tosystems and methods in which the fluid permeability of a porous medium(e.g., a porous solid) can be adjusted by applying an electricalpotential to the porous medium. For example, in some embodiments, thefluid permeability of a porous medium can be decreased by applying anelectrical potential to the porous medium such that material isdeposited over pores of the porous medium, thus blocking the transportof fluid through the thickness of the porous medium. As another example,in some embodiments, the fluid permeability of a porous medium can beincreased by applying an electrical potential to the porous medium(e.g., having a polarity opposite of the polarity of the electricalpotential used to reduce the permeability of the porous medium) suchthat material is removed from the porous medium, thus opening pores ofthe porous medium and allowing for increased transport of fluid throughthe thickness of the porous medium.

The ability to regulate mass transfer across a membrane and other typesof porous media is important in a wide spectrum of engineeringapplications. Despite numerous examples on stimuli-responsive membranesfor liquid-phase species, the ability to regulate mass transfer acrossporous media generally remains elusive for gaseous molecules. Certainembodiments described herein are related to a gas gating mechanismdriven by reversible electrochemical deposition/dissolution of materials(e.g., metals) on electronically conductive porous media, which canmodulate (e.g., continuously modulate) the interfacial fluidpermeability (e.g., gas permeability). In certain embodiments, theinterfacial fluid permeability can be modulated over two orders ofmagnitude. In accordance with certain embodiments, the interfacial fluidpermeability can be modulated without involving moving parts and/or deadvolume, therefore allowing one to design and implement processes thatare otherwise difficult to realize.

Also disclosed herein are systems and methods for capturing species(e.g., acid gases) in which porous media with adjustable fluidpermeabilities are used, for example, to control the flow of fluid intoand out of a medium used to capture the species. For example, in someembodiments, a medium used to capture a species (e.g., a sorbent, anelectrochemical capture medium, etc.) is positioned between twoelectronically conductive porous media. In some embodiments, one of theporous media can define a boundary between the capture medium and afluid stream (e.g., gaseous stream) containing the species one desiresto capture, and the other of the porous media can define a boundarybetween the capture medium and an environment into which one wishes totransfer the captured species. In some such embodiments, the two porousmedia can provide a gating mechanism which effectively preventscross-talk between the stream containing the species to be captured andthe product stream in which the captured species is released. Forexample, in some embodiments, during the capture phase, the first porousmedium may be maintained in a fluid permeable (e.g., gas permeable)state while the second porous medium may be maintained in a fluidimpermeable (e.g., gas impermeable) state, which can allow for exposureof the capture medium to the species that is to be captured. In somesuch embodiments, after a period of time (e.g., after the capture mediumis saturated with the species that is being captured), the first porousmedium may be switched to a fluid impermeable state while the secondporous medium may be switched to a fluid permeable state, which canallow for removal of the captured species from the capture mediumwithout further exposing the capture medium to the source of thecaptured species.

Several of the embodiments described herein are generally described asproviding the ability to control the flow of fluids in general (e.g.,liquids and/or gases), for example, by adjusting a fluid permeability ofa porous medium. One advantage provided by certain of the embodimentsdescribed herein is the ability to adjust gas permeability. In general,adjusting and controlling the gas permeability of a porous medium ismore challenging than adjusting and controlling the liquid permeabilityof a porous medium. The inventors have found, in the context of certainembodiments, that the systems and methods described herein caneffectively allow for the adjustment and control of gas permeabilitiesto an unexpected degree. It should be appreciated that, wherever theadjustment and/or control of fluid permeability is described herein withrespect to a particular embodiment, that embodiment can be used toadjust and/or control gas permeability.

Generally, the fluid permeability of a solid refers to the ability totransport a fluid (e.g., a liquid, a gas) from one boundary of the solidto another boundary of the solid. For example, in the case of a poroussolid comprising pores that bridge a first side and a second side of theporous solid, the fluid permeability refers to the ability to transportfluid from the first side of the porous solid, through the pores of theporous solid, and out of the second side of the porous solid.

Certain aspects are related to devices and methods in which thepermeability of an electronically conductive porous solid is altered.FIGS. 1A-1C are cross-sectional schematic diagrams showingelectronically conductive porous solid 100 whose permeability can bealtered using electrical potentials. FIG. 1D is a perspective viewschematic illustration of electronically conductive porous solid 100.

The electronically conductive porous solid generally comprises poresthat bridge one side of the solid material and a second side of thesolid material. For example, in FIGS. 1A-1D, electronically conductiveporous solid 100 comprises pores 102 that bridge first side 104 ofelectronically conductive porous solid 100 and second side 106 ofelectronically conductive porous solid 100.

The electronically conductive porous solid can be made of any of avariety of suitable materials. Generally, at least one surface of theelectronically conductive porous solid will be sufficientlyelectronically conductive to allow electrical current to be transportedacross the at least one surface to a degree sufficient to allow for theadjustment of the permeability of the electronically conductive poroussolid, as described elsewhere herein. In some embodiments, the bulk ofthe electronically conductive porous solid is electronically conductive.In other embodiments, the bulk of the electronically conductive poroussolid is electronically insulating, but electronically conductivematerial is arranged over one or more surfaces of the solid (e.g., inthe form of a coating) such that electronic conductivity is imparted tothe electronically insulating porous solid. For example, in certainembodiments, to make an electronically insulating porous solidelectrically conductive, a metal is coated on at least one of the firstside and the second side of the electronically insulating porous solid.In some embodiments, the electronically conductive porous solid is atleast partially made of a metal, an electronically conductive ceramic,and/or an electronically conductive polymer. In certain embodiments, itcan be advantageous for the electronically conductive porous solid tocomprise a metal (e.g., in the bulk and/or as an electronicallyconductive overlayer (e.g., coating)). Additional examples ofelectronically conductive porous solid materials are described in moredetail below.

Certain embodiments comprise applying an electrical potential to theelectronically conductive porous solid. Application of an electricalpotential generally comprises applying a voltage difference between theelectronically conductive porous solid and a counter electrode. Forexample, in FIGS. 1B-1C, a voltage difference has been applied betweenthe electronically conductive porous solid 100 and a counter electrode108 to generate an electrical potential. In FIG. 1B, an electricalpotential, having a first polarity 110, has been applied to theelectronically conductive porous solid 100. In FIG. 1C, an electricalpotential, having a second polarity 114 opposite of the first polarity110, has been applied to the electronically conductive porous solid 100.

Certain embodiments comprise adjusting the fluid permeability of theelectronically conductive porous solid. The fluid permeability of theelectronically conductive porous solid can be adjusted, in accordancewith certain embodiments, by applying electrical potentials of differentpolarities to the electronically conductive porous solid. In someembodiments, the fluid permeability of the electronically conductiveporous solid is reduced when an electrical potential, having a firstpolarity, is applied to the electronically conductive porous solid. Forexample, in FIG. 1B, the fluid permeability of the electronicallyconductive porous solid 100 is reduced when an electrical potential,having a first polarity 110, is applied to the electronically conductiveporous solid 100. In some embodiments, the application of the electricalpotential having the first polarity results in the deposition of amaterial on the electronically conductive porous solid. For example, inFIG. 1B, the application of the electrical potential, having the firstpolarity 110, results in the deposition of a material 112 on the secondside 106 of the electronically conductive porous solid 100 such that thepores 102 of the electronically conductive porous solid are at leastpartially blocked. In certain embodiments, the pores of theelectronically conductive porous solid are sized such that the materialdeposited over the pores is larger than the size of the pores to ensurethe ability to adjust the permeability of the electronically conductiveporous solid.

A variety of materials can be deposited over the pores of theelectronically conductive porous solid to adjust the fluid permeabilityof the electronically conductive porous solid. In some embodiments, thematerial deposited on the electronically conductive porous solidcomprises a colloidal particle. In some embodiments, the materialdeposited on the electronically conductive porous solid comprises ametal and/or a metal oxide. For example, in some embodiments, a mediumadjacent to the electronically conductive porous solid comprises a metalsalt dissolved in a solvent (e.g., an aqueous solvent or a non-aqueoussolvent). In some embodiments, the solvent containing the dissolvedmetal salt functions as an electrolyte that can mediate the transport ofcharged species to and from the electrically conductive porous solid. Insome embodiments, the dissolved metal salt comprises metal cations suchthat when an electrical potential is applied to the electricallyconductively porous solid, the metal cations from the medium are reducedat the surface of the electrically conductively porous solid, resultingin the deposition of a metal layer at the surface of the electricallyconductively porous solid. For example, referring to FIG. 1B, inaccordance with some embodiments, a medium 120 adjacent to theelectrically conductive porous solid 100 comprises a metal saltdissolved in a solvent. In some such embodiments, by applying anelectrical potential 110 to the electrically conductive porous solid100, the metal cations in the solvent near the surface of theelectrically conductively solid 100 become reduced such that a material112 is deposited on the second side 106 of the electrically conductiveporous solid 100. It should be understood that the invention is notlimited to the deposition of metal cations, and additional examples ofmaterials that can be deposited over the pores of the electronicallyconductive porous solid are described in more detail below.

In certain embodiments, the fluid permeability of the electronicallyconductive porous solid is increased when an electrical potential,having a second polarity opposite of the first polarity, is applied tothe electronically conductive porous solid. For example, referring toFIG. 1C, in some embodiments, the fluid permeability of theelectronically conductive porous solid 100 is increased when anelectrical potential, having a second polarity 114 opposite of the firstpolarity 110, is applied to the electronically conductive porous solid100. In certain embodiments, when the electrical potential, having thesecond polarity, is applied to the electronically conductive poroussolid, material is removed from the electronically conductive poroussolid. For example, referring to FIG. 1C, in certain embodiments, whenthe electrical potential having the second polarity 114 is applied tothe electronically conductive porous solid 100, material 112 is removedfrom the second side 106 of the electronically conductive porous solid100. Optionally, in some embodiments, when the electrical potentialhaving the second polarity is applied to the electronically conductiveporous solid material is deposited on the counter electrode. Forexample, referring to FIG. 1C, in some embodiments, when the electricalpotential having the second polarity 114 is applied to theelectronically conductive porous solid 100, material 112 is removed fromthe second side 106 of the electronically conductive porous solid 100and subsequently a material 122 is deposited on a counter electrode 108.In some embodiments, the two materials (material 112 and material 122)can comprise the same material. In some embodiments, the two materials(material 112 and material 122) can comprise different materials.

A variety of materials can be removed from the electronically conductiveporous solid to increase the fluid permeability of the electronicallyconductive porous solid. In some embodiments, the material removed fromthe electronically conductive porous solid comprises a colloidalparticle. In some embodiments, the material removed from theelectronically conductive porous solid comprises a metal and/or a metaloxide. In some embodiments, application of the second electricalpotential can cause oxidation and subsequent removal of the materialfrom the electronically conductive porous solid. For example, in someembodiments, the material on the electronically conductive porous solidcomprises a metal (e.g., zinc), and application of the second electricalpotential causes oxidation of the metal to form metal cations (e.g.,zinc cations). The metal cations can be subsequently carried away fromthe electronically conductive porous solid, for example, by a mediumadjacent to the electronically conductive porous solid. For example,referring to FIGS. 1B-1C, in some embodiments, material 112 comprises ametal. In some such embodiments, by applying electrical potential 114 toelectrically conductive porous solid 100, metal 112 can be oxidized tometal cations. In some such embodiments, medium 120 adjacentelectronically conductive porous solid 100 can transport the metalcations away from the electronically conductive porous solid 100 suchthat the pores 102 of electronically conductive porous solid 100 becomeexposed. It should be understood that the invention is not limited tothe removal of metal via the formation of metal cations, and additionalexamples of materials that can be removed from the electronicallyconductive porous solid are described in more detail below.

In some embodiments, the removal and deposition of a material from thesecond side of the electrically conductive porous solid are reversibleprocesses such that the amount of a material removed from theelectrically conductive porous solid constitutes a substantial portionof (e.g., at least 50 wt %, at least 75 wt %, at least 90 wt %, at least95 wt %, or at least 99 wt % of) the amount of a material initiallydeposited on the electrically conductive porous solid.

In certain embodiments, the electronically conductive porous solid canfunction as a gate between a medium that is used to remove species froma gaseous stream (e.g., CO₂ or other acid gases from an exhaust stream).In some such embodiments, the permeability of the electronicallyconductive porous solid can be adjusted such that the medium used toremove species from the gaseous stream is only exposed to the gaseousstream at certain times (e.g., when the medium is not saturated andremains able to capture the species from the gaseous stream).

Accordingly, certain embodiments comprise removal of one or more speciesfrom gaseous stream. A species of interest in the gaseous stream can beselectively removed, in accordance with some embodiments, bysequestering the species from the gas stream using a sequestrationmaterial. In some embodiments, the electronically conductive poroussolid has a first side and a second side, and at least one of the firstside and the second side is in fluid communication with a gaseousstream. For example, referring to FIG. 1A, in accordance with someembodiments, the electronically conductive porous solid 100 has a firstside 104 and a second side 106, and both of the first side 104 and thesecond side 106 are in fluid communication with a gaseous stream 116such that at least a portion of the gaseous stream 116 can pass throughthe pores 102 of the electronically conductive porous solid 100. Incertain embodiments, to sequester the species of interest from thegaseous stream, a sequestration material is disposed adjacent to theelectronically conductive porous solid. For example, referring to FIG.1A, in some embodiments, a sequestration material is disposed adjacentto the electronically conductive porous solid 100 within medium 120 suchthat when a gaseous stream passes through the electronically conductivesolid 100 from the first side 104 to the second side 106, a species fromthe gaseous stream 116 can be selectively sequestered by thesequestration material. Examples of mechanisms by which the species maybe captured by a medium (e.g., electrochemical capture,non-electrochemical capture) are provided in more detail below.

In some embodiments, to prevent the sequestered species from backflowing into the gaseous stream (e.g., as a result of convective masstransfer), the fluid permeability of the electronically conductiveporous solid can be reduced by applying an electrical potential suchthat the second side of the electrically conductive porous solid is nolonger in fluidic communication with the gaseous stream. For example,referring to FIG. 1B, in some embodiments, the fluid permeability of theelectronically conductive porous solid 100 is reduced when theelectrical potential, having a first polarity 110, is applied to theelectronically conductive porous solid 100. The application of theelectrical potential can result in the deposition of a material on theelectronically conductive porous solid 100 such that the second side 106of the electrically conductive porous solid 100 is no longer in fluidiccommunication with the gaseous stream 116. In some embodiments, afterthe permeability of the electronically conductive porous solid 100 hasbeen reduced, captured species within medium 120 can be released.Examples of mechanisms by which captured species may be released by amedium (e.g., electrochemical release, non-electrochemical release) areprovided in more detail below.

In certain embodiments, the degree of fluid permeability of theelectronically conductive porous solid can be controlled by modulatingthe strength of an applied electrical potential, and/or the depositioncapacity of the material deposited on the electronically conductiveporous solid. For example, in accordance with certain embodiments, byincreasing the deposition capacity of a material deposited on theelectronically conductive porous solid, a denser material layer will beformed on the electronically conductive porous solid, resulting in ahigher blockage of the pores that leads to a higher reduction in fluidpermeability of the electronically conductive porous solid.

In some embodiments, the inventive systems and methods described hereinmake use of multiple electronically conductive porous solids. Theelectronically conductive porous solids can be used as gates to controlthe flow of fluid (e.g., gaseous streams) into and out of a regionbetween the electronically conductive porous solids. Examples of suchsystems are shown in FIGS. 2A-2C and 3A-3C, exemplary operations ofwhich are described in more detail below.

FIGS. 2A-2C are cross-sectional schematic diagrams showing a firstelectronically conductive porous solid 200 and a second electronicallyconductive porous solid 201 that is electronically coupled to the firstelectronically conductive porous solid 200. The two electronicallyconductive porous solids can be electronically coupled such that when anelectrical potential is applied, electrical current travels from oneelectronically conductive porous solid to the other electronicallyconductive porous solid and results in a change in fluid permeability inboth electronically conductive porous solids such that the change influid permeability of the first electrically conductive porous solid isopposite to the change in fluid permeability of the second electricallyconductive porous solid. For example, in some cases, application of anelectrical potential can cause an increase in the fluid permeability ofthe first electronically conductive porous solid while simultaneouslycausing a decrease in the fluid permeability of the secondelectronically conductive porous solid. In certain cases, application ofan electrical potential can cause a decrease in the fluid permeabilityof the first electronically conductive porous solid while simultaneouslycausing an increase in the fluid permeability of the secondelectronically conductive porous solid.

In some embodiments, the polarity of the applied electrical potentialcontrols whether the fluid permeability of each electronicallyconductive porous solid increases or decreases. For example, in someembodiments, when an electrical potential having a first polarity withrespect to the first electronically conductive porous solid is applied,the fluid permeability of the first electronically conductive poroussolid decreases while the fluid permeability of the secondelectronically conductive porous solid increases and, when an electricalpotential having a second polarity with respect to the firstelectronically conductive porous solid is applied (the second polaritybeing opposite the first polarity), the fluid permeability of the firstelectronically conductive porous solid increases while the fluidpermeability of the second electronically conductive porous soliddecreases.

The permeability of both the first electronically conductive poroussolid and the second electronically conductive solid can be alteredusing electrical potentials, for example, in a manner similar to thealteration of the fluid permeability of the electronically conductiveporous solid 100 described above with relation to FIGS. 1A-1C. In fact,electronically conductive porous solid 100 may be used as one or both ofelectronically conductive porous solids 200 and 201 in FIGS. 2A-2C,and/or as one or both of electronically conductive porous solids 300 and301 in FIGS. 3A-3C. In this way, electrical potentials can be used toswitch the system illustrated in FIGS. 2A-2C between two states: a firststate in which the first electronically conductive porous solid ispermeable to fluid while the second electronically conductive poroussolid is impermeable to fluid (as shown in FIGS. 2A and 2C) and a secondstate in which the first electronically conductive porous solid isimpermeable to fluid while the second electronically conductive poroussolid is permeable to fluid (as shown in FIG. 2B).

In certain embodiments, both the first electronically conductive poroussolid and the second electronically conductive porous solid comprisepores that bridge one side of the solid material and a second side ofthe solid material. For example, in FIGS. 2A-2C, in accordance withcertain embodiments, the first electronically conductive porous solid200 comprises pores 202 that bridge first side 204 of electronicallyconductive porous solid 200 and second side 206 of electronicallyconductive porous solid 200. Furthermore, the second electronicallyconductive porous solid 201 comprises pores 203 that bridge first side205 of electronically conductive porous solid 201 and second side 207 ofelectronically conductive porous solid 201.

The first electronically conductive porous solid and the secondelectronically conductive porous solid can be made of any of a varietyof suitable materials. Generally, for each of the first electronicallyconductive porous solid and the second electronically conductive poroussolid, at least one surface of the electronically conductive poroussolid will be sufficiently electronically conductive to allow electricalcurrent to be transported across at least one surface to a degreesufficient to allow for the adjustment of the fluid permeability of theelectronically conductive porous solid, as described elsewhere herein.In some embodiments, the bulk of each of the first electronicallyconductive porous solid and the second electronically conductive poroussolid is electronically conductive. In other embodiments, the bulk ofeach of the first electronically conductive porous solid and the secondelectronically conductive porous solid is electronically insulating, butone or more surfaces of each solid is coated with an electronicallyconductive material that imparts conductivity to the electronicallyinsulating porous solid. For example, in certain embodiments, to make anelectronically insulating porous solid electrically conductive, a metalis coated on at least one of the first side and the second side of theelectronically insulating porous solid. In some embodiments, eachelectronically conductive porous solid is at least partially made of ametal, an electronically conductive ceramic, and/or an electronicallyconductive polymer. In certain embodiments, it can be advantageous forat least one of the first electronically conductive porous solid and thesecond electronically conductive porous solid to comprise a metal (e.g.,in the bulk and/or as an electronically conductive coating). In someembodiments, the first electronically conductive porous solid and thesecond electronically conductive porous solid comprise the same metal.In some embodiments, the first electronically conductive porous solidand the second electronically conductive porous solid comprise differentmetals.

In some embodiments, a material can be deposited on a first side of thesecond electronically conductive porous solid. The material can, in someembodiments, be deposited over pores of the second electronicallyconductive porous solid such that its fluid permeability is reduced. Forexample, referring to FIG. 2A, in accordance with some embodiments, thefluid permeability of the second electronically conductive porous solid201 is reduced when an electrical potential 220 is applied to the firstand the second electronically conductive porous solids 200 and 201. Theapplication of the electrical potential 220 can result in the depositionof a material 222 on the second electronically conductive porous solid201 (e.g., over pores of the second electronically conductive poroussolid) such that the second side 207 of the second electricallyconductive porous solid 201 is no longer in fluidic communication withthe medium 230.

Certain embodiments comprise altering an electrical potential appliedbetween the first electronically conductive porous solid and the secondelectronically conductive porous solid. In some such embodiments,altering the electrical potential applied between the firstelectronically conductive porous solid and the second electronicallyconductive porous solid (e.g., by changing the polarity of the appliedelectrical potential) results in the simultaneous alteration of thefluid permeabilities of the first electronically conductive porous solidand the second electronically conductive porous solid. Simultaneous, inthis context, means that over at least a portion of the time duringwhich the electrical potential is applied, material is being removedfrom one of the electronically conductive porous solids while also beingdeposited on the other of the electronically conductive porous solids.In some embodiments, when an electrical potential is applied to thefirst and second electronically conductive porous solids with a firstpolarity, a fluid permeability of the first electronically conductiveporous solid is reduced and a fluid permeability of the secondelectronically conductive porous solid is increased. In certainembodiments, when an electrical potential is applied to the first andsecond electronically conductive porous solids with a second polarityopposite the first polarity, the fluid permeability of the firstelectronically conductive porous solid is increased and the fluidpermeability of the second electronically conductive porous solid isreduced.

For example, referring to FIG. 2B, in accordance with some embodiments,when an electrical potential is applied to the first electronicallyconductive solid 200 and the second electronically conductive poroussolid 201 with a first polarity 210, a fluid permeability of the firstelectronically conductive porous solid 200 is reduced and a fluidpermeability of the second electronically conductive porous solid 201 isincreased. In some embodiments, by altering the electrical potential(e.g., by changing its polarity), a material is deposited over pores ofthe first electronically conductive porous solid such that the fluidpermeability of the first electronically conductive porous solid isreduced, and simultaneously a material is removed from pores of thesecond electronically conductive porous solid such that the fluidpermeability of the second electronically conductive porous solid isincreased. For example, in some embodiments, before applying anelectrical potential with a first polarity 210 to the first and secondelectrically conductive solids 200 and 201, the pores 202 of the firstelectrically conductive porous solid 200 are initially unblocked,whereas the pores 203 of the second electrically conductive porous solid201 are initially at least partially blocked by a material 222 depositedat an interface between the medium 230 and the second electronicallyconductive porous solid 201. One such example of this arrangement isshown in FIG. 2A. Referring to FIG. 2B, in accordance with someembodiments, by applying an electrical potential with a first polarity210 to the first and the second electrically conductive porous solids, amaterial 212 is deposited at an interface between the medium 230 and thefirst electronically conductive porous solid 200 over the pores 202. Insome such embodiments, at the same time that a material 212 is depositedover the pores 202 of the first electronically conductive porous solid200, a material 222 is removed from an interface between the medium 230and the second electronically conductive porous solid 201. In someembodiments, when a material is deposited at an interface between themedium and the first electronically conductive porous solid, the poresof the first electronically conductive porous solid are at leastpartially blocked. In some embodiments, the two materials (material 212deposited on the first electronically conductive porous solid 200 andmaterial 222 deposited on the second electronically porous solid 201)can comprise the same material. In some embodiments, the two materials(material 212 deposited on the first electronically conductive poroussolid 200 and material 222 deposited on the second electronically poroussolid 201) can comprise different materials.

Any of a variety of materials can be deposited over the pores of and/orremoved from the first and second electronically conductive poroussolids. For example, any of the materials described above with respectto electronically conductive porous solid 100 of FIGS. 1A-1C can bedeposited on and/or removed from either or both of first electronicallyconductive porous solid 200 and/or second electronically conductiveporous solid 201 to adjust their fluid permeabilities. In someembodiments, the deposition of material over pores of the firstelectronically conductive porous solid comprises deposition of colloidalparticles over pores of the first electronically conductive poroussolid. In some embodiments, the deposition of material over pores of thefirst electronically conductive porous solid comprises precipitation ofthe material over pores of the first electronically conductive poroussolid. In some embodiments, the material deposited at the interfacebetween the medium and the first electronically conductive porous solidand over the pores of the first electronically conductive porous solidcomprises a metal and/or a metal oxide. For example, in someembodiments, a medium positioned between the first and the secondelectrically conductive porous solid comprises a metal salt dissolved ina solvent (e.g., an aqueous solvent or a non-aqueous solvent). In someembodiments, the metal salt is an electrolyte that can mediate thetransport of charged species between the first and the secondelectronically conductive porous solids. In some embodiments, thedissolved metal salt comprises metal cations such that when anelectrical potential with a first polarity is applied to the first andthe second electrically conductively porous solids, the positive metalions from the medium are reduced at the surface of the firstelectrically conductively porous solid, resulting in the deposition of ametal layer at the surface of the first electrically conductively poroussolid, while the existing metal layer at the surface of the secondelectrically conductively porous solid is simultaneously oxidized intopositive metal ions, resulting in the removal of the metal layer as thepositive metal ions dissolve back into the medium. In certainembodiments, it can be advantageous to select a material that has a fastdeposition and dissolution response under an applied electricalpotential. Additional examples of materials that can be deposited overthe pores of the electronically conductive porous solid are described inmore detail below.

In certain embodiments, when an electrical potential is applied to thefirst and second electronically conductive porous solids with a secondpolarity opposite the first polarity, the fluid permeability of thefirst electronically conductive porous solid is increased and the fluidpermeability of the second electronically conductive porous solid isreduced. For example, in FIG. 2C, when an electrical potential having asecond polarity 220 opposite the first polarity 210 is applied to thefirst electronically conductive solid 200 and the second electronicallyconductive porous solid 201, the fluid permeability of the firstelectronically conductive porous solid 200 is increased and the fluidpermeability of the second electronically conductive porous solid 201 isreduced. In some embodiments, by altering the electrical potential, amaterial is removed from pores of the first electronically conductiveporous solid such that the fluid permeability of the firstelectronically conductive porous solid is increased, and simultaneouslya material is deposited over pores of the second electronicallyconductive porous solid such that the fluid permeability of the secondelectronically conductive porous solid is reduced. For example, incertain embodiments, before applying an electrical potential with asecond polarity 220 opposite the first polarity 210 to the first andsecond electrically conductive solids 200 and 201, the pores 202 of thefirst electrically conductive porous solid 200 are initially at leastpartially blocked by a material 212 deposited at an interface betweenthe medium 230 and the first electronically conductive porous solid 200,whereas the pores 203 of the second electrically conductive porous solid201 are initially unblocked. One such example of this arrangement isshown in FIG. 2B. Referring to FIG. 2C, in accordance with certainembodiments, by applying an electrical potential with a second polarity220 opposite the first polarity 210 to the first and the secondelectrically conductive porous solids 200 and 201, a material 222 isdeposited at an interface between the medium 230 and the secondelectronically conductive porous solid 201 and a material 212 is removedfrom an interface between the medium 230 and the first electronicallyconductive porous solid 200. In some embodiments, when a material isdeposited at an interface between the medium and the secondelectronically conductive porous solid, the pores of the secondelectronically conductive porous solid are at least partially blocked.In some embodiments, the material deposited at the interface between themedium and the second electronically conductive porous solid and overthe pores of the second electronically conductive porous solid comprisesa metal and/or a metal oxide. In some embodiments, the deposition ofmaterial at the interface between the medium and the secondelectronically conductive porous solid and over pores of the secondelectronically conductive porous solid comprises deposition of colloidalparticles over pores of the second electronically conductive poroussolid. In some embodiments, the deposition of material at the interfacebetween the medium and the second electronically conductive porous solidand over pores of the second electronically conductive porous solidcomprises precipitation of the material over pores of the secondelectronically conductive porous solid.

In certain embodiments, the mechanisms associated with the deposition ofa material at an interface between a medium and an electronicallyconductive porous solid can be the same for both of the first and thesecond electronically conductive porous solids. In certain embodiments,the mechanisms associated with the removal of a material from aninterface between a medium and an electronically conductive porous solidcan be the same for both of the first and the second electronicallyconductive porous solids.

As noted above, certain aspects are related to devices and methods inwhich a species of interest from a fluid (e.g., gas) stream is capturedand subsequently released by altering the permeability of anelectrochemical device comprising two electronically conductive poroussolids coupled to each other. The systems and methods described hereincan be used to capture any of a variety of suitable species including,but not limited to, acid gases and/or hydrocarbon gases. In addition,any of a variety of mechanisms for capturing the species can be used,including electrochemical mechanisms and non-electrochemical mechanisms.Additional examples of species that can be captured and released by themedium and additional examples of mechanisms by which species captureand release can be achieved are described in more detail below. Examplesof systems and methods comprising multiple electronically conductiveporous solids that can be used to capture species of interest are nowdescribed, with reference to FIGS. 2A-2C and FIGS. 3A-3C.

In some embodiments, the first electronically conductive porous solidhas a first side and a second side, and at least one of the first sideand the second side is in fluid communication with a fluid stream. Forexample, in FIG. 2A, the first electronically conductive porous solid200 has a first side 204 and a second side 206, and both of the firstside 204 and the second side 206 are in fluid communication with a fluidstream 216 adjacent to the first side 204 such that at least a portionof the fluid stream 216 can pass through the pores 202 of the firstelectronically conductive porous solid 200.

Certain embodiments comprise transporting a fluid through pores of thefirst electronically conductive porous solid. For example, in FIG. 2A,fluid 216 is transported through pores 202 of first electronicallyconductive porous solid 200. The fluid that is transported through thepores of the first electronically conductive porous solid may be in theform of a liquid and/or a gas. The fluid may be in the form of a purefluid or a fluid containing one or more other components (e.g., ions,solids, other fluids of a different chemical composition, combinationsof these, and the like). In certain embodiments, it can be particularlyadvantageous to use the systems and methods described herein to capturespecies of interest from fluids containing one or more gases. It hasbeen found that certain of the systems and methods described herein canbe used to achieve species capture from gaseous streams whilesubstantially reducing (or eliminating) crosstalk between the inletstream from which the species is captured and an outlet streamcontaining the released species.

In certain embodiments, to capture a species of interest from the fluidstream, a medium is positioned adjacent to the first electronicallyconductive porous solid. The medium can be positioned, for example,between the first electronically conductive porous solid and the secondelectronically conductive porous solid. For example, referring to FIG.2A, in some embodiments, a medium 230 is disposed between the firstelectronically conductive porous solid 200 and the second electronicallyconductive porous solid 201 such that when a fluid stream 216 passesthrough the first electronically conductive solid 200 (from the firstside 204 to the second side 206), a species from the fluid stream can beselectively captured by the medium 230.

Certain embodiments comprise releasing the species from the medium suchthat the species is transported through the second electronicallyconductive porous solid. As described elsewhere herein, the fluidpermeability of the first and the second electrically conductive poroussolids can be adjusted (in certain cases, simultaneously) by applying anelectric potential to the first and the second electrically conductiveporous solids such that a material is deposited at an interface betweenthe medium and either the first or the second electrically conductiveporous solid to at least partially block the pores of eitherelectronically conductive porous solid. For example, referring to FIG.2A, in certain embodiments, the pores 203 on the second electricallyconductive porous solid 201 are, initially, at least partially blockedby a material 222 deposited at an interface between the medium 230 andthe second electrically conductive porous solid 201 such that thespecies captured by the medium 230 cannot be transported through thesecond electronically conductive porous solid. In some embodiments,referring to FIG. 2B, by applying an electrical potential 210 (which hasa different polarity than electrical potential 220 applied in FIG. 2A),the material 222 deposited at an interface between the medium 230 andthe second electrically conductive porous solid 201 is removed such thatthe pores 203 on the second electrically conductive porous solid 201 areno longer blocked and such that a the species captured by the medium 230can be released through the second electronically conductive poroussolid 201.

In certain embodiments, the first and the second electronicallyconductive porous solids can function as gates to the medium during thecapture of a species from a fluid (e.g., gas such as CO₂ or other acidgases from an exhaust stream) and the release of a species (e.g., into aproduct stream). For example, certain embodiments comprise applying anelectrical potential to the electronically conductive porous solids suchthat a species from a fluid can enter through the first electronicallyconductive porous solid and can be subsequently captured by the medium.In FIG. 2A, for example, an electrical potential 220 has been applied toelectronically conductive porous solids 200 and 201 such that a speciesfrom fluid stream 216 can enter through the first electronicallyconductive porous solid 200 and can be subsequently captured by medium230.

In some embodiments, once the medium has captured the desired amount ofspecies from the fluid (e.g. when the medium is saturated with thespecies), an electrical potential with a different polarity is appliedsuch that the pores of the first electronically conductive porous solidbecome blocked (thus cutting off fluid communication between an inletstream and the medium) and such that the pores of the secondelectronically conductive porous become unblocked (allowing for therelease of species from the medium to an outlet stream). In some suchembodiments, the fluid permeability of the first and the secondelectronically conductive porous solids can be adjusted such that themedium used to capture and release the species is in fluidiccommunication with a product stream separate from the input stream thatoriginally contained the captured species without also being in fluidiccommunication with the input stream. For example, in FIG. 2B, the fluidpermeabilities of the first and the second electronically conductiveporous solids 200 and 201 have been adjusted relative to the fluidpermeabilities of the first and the second electronically conductiveporous solids 200 and 201 in FIG. 2A, such that, in FIG. 2B, medium 230used to capture and release the species from stream 216 is in fluidiccommunication with product stream 217 (which is separate from the inputfluid stream 216) and is also not in fluidic communication with theinput fluid stream 216. To illustrate one exemplary mode of operationwith reference to FIGS. 2A-2B, in some embodiments, once medium 230 hascaptured a desired amount of species from fluid stream 216, anelectrical potential having a different polarity 210 can be applied toelectronically conductive porous solids 200 and 201. Application of theelectrical potential having a different polarity 210 can result in thepores of first electronically conductive porous solid 200 becomingblocked, thus cutting off fluid communication between inlet stream 216and medium 230. In addition, application of the electrical potentialhaving a different polarity 210 can result in the pores of the secondelectronically conductive porous become unblocked, allowing for therelease of species from medium 230 to outlet stream 217.

As noted above, certain embodiments comprise the use of a medium tocapture and/or release species from a fluid (e.g., gaseous) stream. Forexample, referring back to FIGS. 1A-1C, in certain embodiments, medium120 can be used to capture and/or release one or more species fromstream 116. Also, referring to FIGS. 2A-2C, in some embodiments medium230 can be used to capture and/or release one or more species fromstream 216. Referring to FIGS. 3A-3C, in certain embodiments, medium 330can be used to capture and/or release one or more species from stream316.

Capture and release of species can be achieved using any of a variety ofmechanisms. In certain embodiments, the medium comprises a sequestrationmaterial. In some embodiments, the sequestration material can capturespecies via a non-electrochemical mechanism. Examples of suitablenon-electrochemical mechanisms include, but are not limited to,adsorption, absorption, and/or a non-electrochemical chemical reaction.Electrochemical capture mechanisms, described in more detail below, canalso be used.

In some embodiments, the sequestration material comprises a zeolite, ametal-organic framework, a resin, and/or an electrolyte. Additionalexamples of sequestration material capture medium are described in moredetail below.

In some embodiments, the sequestration material is in the mediumpositioned between the first and second electrically conductive poroussolid. The sequestration material can be disposed in the medium by anyknown physical and/or chemical means. For example, the sequestrationmaterial can be disposed in the medium via any physical and chemicalinteractions with the medium (e.g., embedding, adsorbing, reacting). Forexample, referring to FIGS. 2A-2C, in some embodiments, a sequestrationmaterial is in the medium 230 positioned between the first and thesecond electrically conductive porous solids 200 and 201. In some suchembodiments, when a fluid stream 216 (e.g., a gaseous stream) passesthrough the pores 202 of the first electrically conductive porous solid200, the sequestration material selectively captures a species from thefluid stream 216 via non-electrochemical mechanism, such as adsorption,absorption, and/or a non-electrochemical chemical reaction.

Certain embodiments comprise releasing a species from the sequestrationmaterial by exposing the medium to a stimulus such as a change inchemical and/or physical conditions. In some embodiments, the stimuluscomprises a change in temperature and/or pressure. For example, incertain embodiments, a species could be absorbed to the sequestrationmaterial at an initial temperature that is associated with a highcapture affinity (e.g., a high adsorption affinity, a high absorptionaffinity, a high rate of chemical reaction that results in the captureof the species, and the like) between the sequestration material and thespecies, and subsequently released from the sequestration material at asecond temperature that that is associated with a low capture affinity(e.g., a low adsorption affinity, a low absorption affinity, a high rateof chemical reaction that results in the release of the species, and thelike) between the sequestration material and the species. In certainembodiments, a species can be captured by the sequestration material ata first partial pressure that favors the capture of the species by thesequestration material, and then released at a second partial pressure(e.g., by applying a vacuum) that favors the release of the species fromthe sequestration material. Other mechanisms of non-electrochemicalcapture and release are also possible.

The present disclosure is not limited to embodiments in which the mediumcaptures species non-electrochemically, and in some embodiments, themedium can electrochemically capture one or more species. For example,in some embodiments, the medium comprises a first electrode and a secondelectrode such that the medium can capture the species of interest froma fluid via an electrochemical mechanism (e.g., an electrochemicalreaction between the species one wishes to capture and/or release and anelectrochemically active material). For example, in FIGS. 3A-3C, a firstelectrode 312 and a second electrode 313 coupled to the first electrode312 are positioned in the medium 330 between a first electricallyconductive porous solid 300 and second electrically conductive poroussolid 301. The properties of the first and the second electricallyconductive porous solids 300 and 301 can be the same as those describedelsewhere herein with respect to FIGS. 2A-2C. In some embodiments, byapplying a first electrical potential between the first electrode andthe second electrode of the medium (also described herein as the “mediumelectrical potential”), the species from the fluid is electrochemicallycaptured by the medium. For example, in FIG. 3A, by applying a firstmedium electrical potential 340 between a first electrode 312 and asecond electrode 313, a species from a fluid stream 316 (e.g., a gas)that passes through the pores of the first electrically conductiveporous solid 300 can be electrochemically captured by the medium 330.While the first and the second electrodes 312 and 313 are illustrated asbeing in the same material used to facilitate the adjustment of thepermeability of porous solids 300 and 301 in FIGS. 3A-3C, in otherembodiments, the first and the second electrodes 312 and 313 can be in amaterial that is different from the material used to facilitate theadjustment of the permeability of porous solids 300 and 301 in FIGS.3A-3C (e.g., such as a second liquid material located within a firstliquid material, all of which may be part of medium 330). In certainembodiments, the medium further contains a material that iselectrochemically activated such that a species of interest can bind tothe electrochemically activated form of the material. In certainembodiments, by applying an electrical potential having a first polarityto the first medium electrode and the second medium electrode, theelectrochemically active material in the medium undergoes oxidation orreduction and such that it forms a complex with the species of interest,thus capturing the species of interest. Additional examples of materialsthat can electrochemically capture the species are described in moredetail below.

In certain embodiments, by applying a second medium electrical potentialbetween the first electrode and the second electrode of the medium, thesecond medium electrical potential having a polarity that is theopposite of the polarity of the first medium electrical potential, thespecies captured by the medium can be released by the medium. Forexample, in FIG. 3B, by applying a second medium electrical potential350 between a first electrode 312 and a second electrode 313, a speciescaptured by the medium 330 can be electrochemically released by themedium 330. In certain embodiments, with the application of a secondmedium electrical potential, the material in the medium undergoes eitheroxidation or reduction, thus resulting in release (e.g., viadissociation) of the species of interest.

In some embodiments, the medium used to capture the species is in fluidcommunication with the outside environment via only one of the firstelectronically conductive porous solid and the second electronicallyconductive porous solid during species capture and during speciesrelease. For example, in certain embodiments, during the process ofcapturing the species from the input stream (e.g., input fluid stream216 in FIGS. 2A and 2C, input fluid stream 316 as shown in FIG. 3A andFIG. 3C), the medium is in fluid communication with the outsideenvironment only via first electronically conductive medium. Examples ofsuch operation are shown, for example, in FIGS. 2A, 2C, 3A, and 3C. Insome embodiments, during the process of releasing the species from themedium into an outlet stream (e.g., stream 217 in FIG. 2B, stream 317 inFIG. 3B), the medium is in fluid communication with the outsideenvironment only via second electronically conductive medium. Examplesof such operation are shown, for example, in FIGS. 2B and 3B.

In certain embodiments in which electrochemical capture and release of atargeted species is employed, the operation of the electrodes within themedium (used to electrochemically capture the species) and the operationof the first and the second electronically conductive solids (used tocontrol which external fluid is in fluidic communication with themedium) are coupled, for example to allow for continuous capture andrelease of a species from a fluid being transported into the medium. Forexample, in some embodiments, the system can be operated in a “capturemode,” during which an electrical potential can be applied to the firstand second electronically conductive porous solids such that the firstelectronically conductive porous solid remains fluid permeable (thusestablishing or maintaining fluidic communication between the capturemedium and the input fluid stream containing the species of interest)and the second electronically conductive porous solid remains fluidimpermeable. Also, in “capture mode,” a first medium electricalpotential can be applied to the first and the second electrodes withinthe medium such that a material in the medium is electrochemicallyactivated to capture the species that is transported into the medium. Toillustrate, referring to FIG. 3A, in certain embodiments, an electricalpotential 320 can be applied to the first and second electronicallyconductive porous solid 300 and 301 such that first electronicallyconductive porous solid 300 remains fluid permeable (thus establishingor maintaining fluidic communication between medium 330 and input stream316 containing the species of interest) and the second electronicallyconductive porous solid 301 remains fluid impermeable. Also, a firstmedium electrical potential 340 can be applied to the first and thesecond electrodes 312 and 313 within medium 330 such that a material inmedium 330 is electrochemically activated to capture the species that istransported into the medium via stream 316.

In some embodiments, once the medium captures a certain amount ofspecies (e.g., when the medium is saturated with the species, or whenthe medium otherwise captures a desired amount of the species), thepolarities of the applied electrical potentials can be altered such thatthe system is operated in “release mode.” During release mode, anelectrical potential can be applied to the first and secondelectronically conductive porous solids such that the firstelectronically conductive porous solid is rendered fluid impermeable(thus cutting off fluidic communication between the capture medium andthe input fluid stream containing the species of interest) and thesecond electronically conductive porous solid can be rendered fluidpermeable (thus establishing fluidic communication between the mediumand an outlet stream). Also, in “release mode” a medium electricalpotential can be applied to the first and the second electrodes withinthe medium such that a material in the medium is electrochemicallyactivated to release the species that was captured during capture mode.To illustrate, referring to FIG. 3B, in certain embodiments, anelectrical potential 310 can be applied to the first and secondelectronically conductive porous solids 300 and 301 such that firstelectronically conductive porous solid 300 is rendered fluid impermeable(thus cutting off fluidic communication between medium 330 and inputstream 316 containing the species of interest) and the secondelectronically conductive porous solid 301 is rendered fluid permeable(thus establishing fluidic communication between the medium and anoutlet stream). Also, in FIG. 3B, medium electrical potential 350 can beapplied to the first and the second electrodes 312 and 313 within medium330 such that a material in medium 330 is electrochemically activated torelease the species that was capture by the medium 330 during capturemode, which can be subsequently transported out of medium 330 via stream317.

In some embodiments, the process of species capture and release can berepeated. Referring to FIG. 3C, in accordance with certain embodiments,the electrical potentials of the both the electronically conductiveporous solid and the electrodes within the medium can be adjusted torepeat “capture mode” operation. For example, referring to FIG. 3C, inaccordance with certain embodiments, with the application of electricalpotential 320, an alternation of fluid permeability occurs such that thepores 302 of the first electronically conductive porous solid are opento fluid stream 316 (e.g., a gas), in a manner similar to thatillustrated in FIG. 3A. Similarly, referring to FIG. 3C, a material inthe medium 330 can be electrochemically activated to capture the speciesthat is transported through the first electronically conductive poroussolid 301.

In some embodiments, the electrodes within the medium can be coupled tothe electronically conductive porous solids in a way that allows anautomated adjustment of fluid permeability of the electronicallyconductive porous solids during species capture and release.

In some embodiments, the medium comprises an electrolyte that canfacilitate the transfer of a species to an electrochemically activatedmaterial (e.g., a material that can undergo redox reaction) in themedium to participate in the capture and release of the species. In someembodiments, the same electrolyte can be shared between the electrodesin the medium and the electronically conductive porous solids such thatthe electrolyte can facilitate both the transfer of charged species tothe electronically conductive porous solids to modulate fluidpermeability (e.g. via deposition/removal of a material under an appliedelectrical potential as described elsewhere herein) and the transfer ofthe species to the electrodes in the medium to facilitate the captureand release of the species (e.g., via electrochemical processes such asredox reactions). For example, in accordance with certain embodiments,the electrolyte permits the diffusion of a species (e.g., CO₂) from afluid (e.g., a gas) through the medium to and away from theelectrochemically activated material in the medium during the speciescapture and release process.

In some embodiments, a first redox potential is associated with theelectrochemical capture and release of a species by a material that canbe electrochemically activated to bind and unbind a species of interest.In some embodiments, a second redox potential is associated with theelectrochemical deposition and removal of a material from theelectronically conductive porous solid as described elsewhere herein. Insome embodiments, the first redox potential of the speciescapture/release process is energetically more favorable than secondredox potential of a material deposited/removed from the electronicallyconductive porous solid.

Certain embodiments comprises electrochemically capturing and releasinga species (e.g., CO₂) from a fluid (e.g., gas) using a material that canreversibly bind and unbind the species via an electrochemical process(e.g., redox reaction). For example, a species of interest (e.g., CO₂)can be carried by an electrolyte through the medium to bindelectrochemically to material in the medium. The material (e.g.,quinones) can subsequently selectively bind to the species (e.g., CO₂)to form stable adducts as the material (e.g., quinones) undergoesreduction by a first medium electrical potential. In certainembodiments, once a certain binding capacity has been reached (e.g.,quinones are saturated by CO₂), a second electric potential can beapplied to oxidize the material (e.g., quinones) such that the species(e.g., CO₂) can dissociate from the material (e.g., quinones) andsubsequently diffuse through the electrolyte to be released to an outletstream.

In some embodiments, the material (e.g., quinones) that can reversiblybind and unbind a species of interest (e.g., CO₂) is deposited on afirst electrode to form a composite electrode. For example, thecomposite electrode can comprise a porous structure such that anelectrolyte in the medium can permeate through the pores to facilitatethe diffusion of a dissolved species (e.g., CO₂) both to and away fromthe composite electrode. With the application of electric potentials ofdifferent polarities, the dissolved species (e.g., CO₂) in theelectrolyte can either bind or unbind from the material (e.g., quinones)on the composite electrode. For example, referring to FIG. 3A, inaccordance with certain embodiments, the medium comprises a firstelectrode 312 (e.g., a composite comprising poly(1,4-anthraquinone)casted or otherwise deposited on carbon nanotubes) and a secondelectrode 313 (e.g., an LiFePO₄ counter electrode). In some embodiments,when a first medium potential 340 has been applied to the first and thesecond electrodes 312 and 313, the material (e.g., quinones) on thefirst electrode 312 becomes reduced and binds to the species (e.g., CO₂)dissolved in the electrolyte in the medium 330. Now referring to FIG.3B, once the material (e.g., quinones) is saturated with the species(e.g. CO₂), a second medium potential (350) can be applied to the firstand second electrodes to dissociate CO₂ from the material (e.g.,quinones) on the composite electrode 312.

In accordance with certain embodiments, electronically conductive poroussolids can be coupled to the first and second electrodes to gate thespecies capture and release process that occurs within the medium. Insome embodiments, the medium comprises metal ions (e.g. Zn⁺²) thatparticipate in the deposition and removal of a metal layer (e.g. Zn) onthe electronically conductive solids as described elsewhere herein. Forexample, referring to FIG. 3A, in accordance with certain embodiments,during the species (e.g., CO₂) capturing process, a material 324 (e.g.,a metal layer comprising Zn) can be deposited on a second electronicallyconductive porous solid 301 to prevent diffusion of the species (e.g.,CO₂) out of the medium 303 through the second electronically conductiveporous solid 303. During the species release process as shown in FIG.3B, the material 324 (e.g., a metal layer comprising Zn) can be removedfrom the second electronically conductive solid 301 while a material 322(e.g., metal layer comprising Zn) can be deposited on the firstelectronically conductive solid 300 such that the species (e.g. CO₂)dissociated from the material (e.g., quinones) can be released into theoutlet stream 317. In some embodiments, the two materials (material 322deposited on the first electronically conductive porous solid 300 andmaterial 324 deposited on the second electronically porous solid 301)can comprise the same material. In some embodiments, the two materials(material 322 deposited on the first electronically conductive poroussolid 300 and material 324 deposited on the second electronically poroussolid 301) can comprise different materials.

Examples of electrochemically-induced CO₂ capture and release processesare described, for example, in U.S. Pat. No. 10,464,018; issued on Nov.5, 2019; and entitled “Electrochemical Process for Gas Separation,”which is incorporated herein by reference in its entirety for allpurposes.

As noted above, in certain of the systems and methods described herein,material can be deposited over pores of an electrically conductive solidand/or removed from over pores of an electronically conductive solidmaterial to alter its fluid permeability. Those of ordinary skill in theart, given the guidance provided by this specification, would be capableof selecting materials that could be used to adjust the permeability ofan electronically conductive porous solid. In some embodiments, thematerial comprises colloidal particles. Non-limiting examples of suchcolloidal particles include but are not limited to inorganic colloidalparticles such as metallic particles (e.g., Au, Ag, etc.), metal oxideparticles (e.g., silica, iron oxide, etc.), carbon-based particles,insoluble salt particles, metal hydroxides, metal sulfides, andpolymeric particles (e.g., polystyrene, latex, etc.). Non-limitingexamples of electrolytes that could be used to facilitate the transportof the colloidal particles between electronically conductive poroussolids include but are not limited to any aqueous and non-aqueouselectrolytes with supporting ionic species.

In some embodiments, the material comprises a metal. For example, insome embodiments, a metal can be plated and deplated from anelectronically conductive solid material to adjust the fluidpermeability of the electronically conductive solid material.Non-limiting examples of metals that can be deposited include but arenot limited to Zn, Mg, Na, and Li. In some embodiments, the materialcomprises a metal oxide. Non-limiting examples of metal oxides that canbe deposited include but are not limited to zinc oxide, aluminum oxide,iron oxide, nickel oxide, manganese oxide, copper oxide, and/or othertransition metal oxides. In some embodiments, the material comprises ametal hydroxide (e.g., zinc hydroxide, aluminum hydroxide, etc.).Non-limiting examples of electrolytes that could be used to facilitatethe transport of metal/metal oxides between electronically conductiveporous solids include but are not limited to any aqueous and non-aqueouselectrolytes comprising precursors of the metal/metal oxide/metalhydroxide.

As noted above, certain of the systems and methods described comprise amedium that comprises metal salt dissolved in a solvent (e.g., anaqueous solvent or a non-aqueous solvent). Examples of metal salts thatcan be used for this purpose include, but are not limited to, metalsalts comprising metal cations (e.g., Zn, Na, Mg, etc.) complexed withanions (e.g., fluoride, chloride, bromide, iodide, hydroxide, nitrate,nitrite, sulfate, sulfite, phosphate, perchlorate, carbonate, acetate,hexafluorophosphate, triflate, bis(trifluoromethanesulfonyl)imide,etc.). The medium can also comprise non-metal salts. Non-metal saltsthat can be used for this purpose include, but are not limited to,non-metal salts comprising non-metal cations (e.g., ammonium cations,etc.) and anions (e.g., fluoride, chloride, bromide, iodide, hydroxide,nitrate, nitrite, sulfate, sulfite, phosphate, perchlorate, carbonate,acetate, hexafluorophosphate, triflate,bis(trifluoromethanesulfonyl)imide, etc.). In some embodiments, thesolvent is a non-aqueous solvent. Examples of non-aqueous solvents thatcan be used include, but are not limited to, alcohols (e.g., ethanol,propanol, etc.), carbonates (e.g., propylene carbonate, dimethylcarbonate, diethyl carbonate, ethylene carbonate, etc.), ethers (e.g.,dimethoxyethane, dioxolane, etc.), acetonitrile, dimethylformamide,dimethyl sulfoxide, ethylene glycol, glycerol, and ionic liquids.

Some embodiment comprises adjusting the permeability of theelectronically conductive porous solids via the deposition anddissolution of a metal (e.g., Zn) deposited on top of the electronicallyconductive porous solid. In some embodiments, a medium comprises a metalsalt (e.g., zinc bis(trifluoromethane sulfonyl) imide) dissolved in anon-aqueous solvent (e.g., propylene carbonate).

Those of ordinary skill in the art, given the guidance provided by thepresent disclosure, would be capable of selecting combinations ofsolvents, deposited and removed species, and dissolved salts that wouldallow for the permeability adjustments of the electronically conductiveporous solids described herein. For example, in certain embodiments inwhich Zn is deposited and removed from the electronically conductiveporous solid to adjust the fluid permeability, a zinc-containing salt(e.g., zinc bis(trifluoromethane sulfonyl) imide, zinc chloride, zincnitrate, zinc sulfate, zinc triflate, etc.) can be dissolved in asolvent capable of dissolving the salt (e.g., water and non-aqueoussolvents such as alcohols (e.g., ethanol, propanol, etc.), carbonates(e.g., propylene carbonate, dimethyl carbonate, diethyl carbonate,ethylene carbonate, etc.), ethers (e.g., dimethoxyethane, dioxolane,etc.), acetonitrile, dimethylformamide, dimethyl sulfoxide, ethyleneglycol, glycerol, etc.). Similarly, in certain embodiments in which Nais deposited and removed from the electronically conductive porous solidto adjust the fluid permeability, a sodium-containing salt (e.g., sodiumbis(trifluoromethanesulfonyl) imide, sodium chloride, sodium nitrate,sodium sulfate, sodium triflate) can be dissolved in a solvent capableof dissolving the salt (e.g., water and non-aqueous solvents such asalcohols (e.g., ethanol, propanol, etc.), carbonates (propylenecarbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate,etc.), ethers (dimethoxyethane, dioxolane, etc.), acetonitrile,dimethylformamide, dimethyl sulfoxide, ethylene glycol, glycerol, etc.).Similar combinations can be used for other embodiments in which othermetal materials (e.g., Mg, Li, etc.) are being deposited on and removedfrom the electronically conductive porous solids. For example, in orderto deposit and remove a metal oxide (e.g., manganese oxide) on and fromthe electronically conductive porous solid, a manganese-containing salt(e.g., manganese chloride, nitrate, sulfate, permanganate, etc.) can bedissolved in a solvent capable of dissolving the salt (e.g., water,alcohols (ethanol, propanol, etc.), carbonates (propylene carbonate,dimethyl carbonate, diethyl carbonate, ethylene carbonate, etc.), ethers(dimethoxyethane, dioxolane, etc.), acetonitrile, dimethylformamide,dimethyl sulfoxide, ethylene glycol, glycerol, etc.). Similarcombinations of metal oxide/metal salt/solvent can be used for thedeposition of other metal oxides. In some embodiments, the depositionand removal of colloidal particles on and from the electronicallyconductive porous solid can be facilitated by combinations of solvents,colloidal species, and dissolved salts. For example, charged silicaparticles can be dispersed in a solvent capable of forming stabledispersion of the particle (e.g., water, alcohols (etc., ethanol,propanol, etc.), carbonates (e.g., propylene carbonate, dimethylcarbonate, diethyl carbonate, ethylene carbonate, etc.), ethers (e.g.,dimethoxyethane, dioxolane, etc.), acetonitrile, dimethylformamide,dimethyl sulfoxide, ethylene glycol, glycerol, etc.) together withsupporting salt species (e.g., metal or ammonium as cations withfluoride, chloride, bromide, iodide, hydroxide, nitrate, nitrite,sulfate, sulfite, phosphate, perchlorate, carbonate, acetate,hexafluorophosphate, triflate, bis(trifluoromethanesulfonyl)imide, etc.as anions) to render the solvent ionically conductive. Similarcombinations of colloidal species/salts/solvent can be used for thedeposition of other colloidal particles.

As noted above, certain of the systems and methods described herein canbe used to capture one or more species from a fluid (e.g., gas) stream.In some embodiments, the species comprises an acid gas. Examples of acidgases that can be captured, in accordance with certain embodiments,include but are not limited to carbon dioxide (CO₂), sulfur monoxide(SO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), hydrogen sulfide(H₂S), sulfur trioxide (SO₃), nitric oxide (NO), nitrous oxide (N₂O),dinitrogen trioxide (N₂O₃), dinitrogen tetroxide (N₂O₄), dinitrogenpentoxide (N₂O₅), and/or carbonyl sulfide (COS). In some embodiments,the acid gas comprises at least CO₂. In some embodiments, the speciescomprises a hydrocarbon gas. Examples of hydrocarbon gases that can becaptured, in accordance with certain embodiments, include but are notlimited to alkanes, alkenes, alkynes, and the like.

As noted above, certain of the systems and methods described herein canbe used to capture one or more species from a fluid (e.g., gas) streamvia a non-electrochemical process. In some embodiments, thesequestration material comprises a zeolite, a metal-organic framework, aresin, and/or an electrolyte. In embodiments in which the sequestrationmaterial captures the species of interest via a non-electrochemicalmechanism, the non-electrochemical mechanism can involve absorption,adsorption, and/or a non-electrochemical chemical reaction. Those ofordinary skill in the art, given the guidance provided by the presentdisclosure, would be capable of selecting sequestration materials thatcould be used to capture specific species of interest. For example, forreversibly capturing and releasing carbon dioxide, alkali metal borates,zeolites, metal-organic frameworks, covalent-organic frameworks, amines,organic solvents, and/or ionic liquids could be used. As anotherexample, for reversibly capturing and releasing various hydrocarbons(e.g., methane, ethane, butane, etc.), zeolites, metal-organicframeworks, covalent-organic frameworks, organic solvents, and/or ionicliquids could be used.

As noted above, certain of the systems and methods described herein canbe used to electrochemically capture one or more species from a fluid(e.g., gas) stream. Those of ordinary skill in the art, given theguidance provided by the present disclosure, would be capable ofselecting electrochemically activated capture media materials that couldbe used to capture specific species of interest. For example, forreversibly capturing and releasing carbon dioxide and/or other acidgases, poly(1,4-anthraquinone), benzoquinone, naphthoquinone,anthraquinone, phenanthrenequinone, organic disulfides, bipyridines,imides, quinoxalines, and/or their derivatives could be used. Forreversibly capturing and releasing sulfur dioxide,poly(1,4-anthraquinone), benzoquinone, naphthoquinone, anthraquinone,phenanthrenequinone, organic disulfides, bipyridines, imides,quinoxalines, and/or their derivatives could be used.

As noted above, certain of the systems and methods described herein canmake use of one or more electronically conductive porous solids (e.g.,electronically conductive porous solid 100 in FIGS. 1A-1D;electronically conductive porous solids 200 and 201 in FIGS. 2A-2C;and/or electronically conductive porous solids 300 and 301 in FIGS.3A-3C). Examples of materials that can be used to form all or part ofthe electronically conductive solid include but are not limited to metal(e.g., gold, copper, platinum, silver, chromium, titanium, aluminum,nickel, stainless steel), electronically conductive ceramic (e.g.,indium tin oxide, fluorine doped tin oxide, etc.), and/or electronicallyconductive polymer (e.g., polypyrrole, polyaniline, polyacetylene,polythiophene, etc.). The electronically porous solid porous solid cancomprise, in some embodiments, non-conductive porous solid at leastpartially coated with an electronically conductive material (e.g., anyof the electronically conductive materials noted above). Examples ofnon-conductive porous solids include but are not limited to metal and/ormetalloid oxides (e.g., anodic aluminum oxide (AAO), silicon dioxide,zinc oxide, zirconium oxide, etc.), electronically insulating polymers,and the like.

In some embodiments, at least one surface of the electronicallyconductive porous solid(s) can have relatively low sheet resistance. Thesurface with the relatively low sheet resistance can span a face of theelectronically conductive porous solid such that application of avoltage to the surface alters (e.g., increases or decreases, asdescribed elsewhere herein) the through-thickness fluid permeability ofthe electronically conductive porous solid. The sheet resistance of asurface of an electronically conductive porous solid is generallymeasured using a four-point probe, where current is applied between twoof the probes (one positioned on either side of the thickness of theelectronically conductive porous solid) and voltage is measured betweenthe other two probes using a voltmeter. In some embodiments, at leastone surface of the electronically conductive porous solid(s) has a sheetresistance of less than 1000 mOhm/sq, less than 100 mOhm/sq, less than10 mOhm/sq, less than 1 mOhm/sq, less than 0.1 mOhm/sq, less than 0.01mOhm/sq, less than 0.001 mOhm/sq, or less than 0.0001 mOhm/sq. Otherranges are also possible.

In some embodiments, the pores of the electronically conductive poroussolid(s) can have relatively low tortuosities. The tortuosity (or τ) ofa pore is generally defined as the ratio of the true length of the pore(L_(pore)) to the length of the line segment connecting ore, one end ofthe pore to the other end of the pore (H); or, τ=L_(pore)/H. Forexample, FIG. 4A shows a relatively highly tortuous pore 401A within anelectronically conductive porous solid; FIG. 4B shows a moderatelytortuous pore 401B within an electronically conductive porous solid; andFIG. 4C shows a perfectly straight pore 401C within an electronicallyconductive porous solid with a tortuosity of exactly 1. In FIGS. 4A, 4B,and 4C, L_(pore) is indicated by 402 and H is indicated by 404. In someembodiments, the electronically conductive porous solid comprises poreshaving a tortuosity of less than or equal to 3.0, less than or equal to2.5, less than or equal to 2.0, less than or equal to 1.75, less than orequal to 1.5, less than or equal to 1.4, less than or equal to 1.3, lessthan or equal to 1.2, or less than or equal to 1.1. Other ranges arealso possible.

U.S. Provisional Patent Application No. 63/002,490, filed Mar. 31, 2020,and entitled “Porous Medium with Adjustable Fluid Permeability andAssociated Systems and Methods,” is incorporated herein by reference inits entirety for all purposes. Yayuan Liu, et al., “Electrochemicallymediated gating membrane with dynamically controllable gas transport,”Sci. Adv. 2020, Vol. 6 (DOI: 10.1126/sciadv.abc1741) is alsoincorporated herein by reference in its entirety for all purposes.

The following example is intended to illustrate certain embodiments ofthe present invention, but does not exemplify the full scope of theinvention.

EXAMPLE

This example describes an electrochemically-mediated carbon dioxideconcentrator in which gating membranes are integrated with redox-activecarbon dioxide sorbents. In this example, the gating mechanismeffectively prevented cross-talk between feed and product gas streamsfor high-efficiency, directional carbon dioxide pumping. This concept ofdynamically regulating transport at gas-liquid interfaces can begenerally applied to a number of systems, including those in the fieldsof gas separations, miniaturized devices, multiphase reactors, and thelike.

The design of stimuli-responsive gating membranes capable of regulatingsubstance transport at the nanoscale is a subject of intense research,motivated by the broad potential impact on science and technology. Todate, a wide variety of functional membranes have been investigated withtunable permeability/selectivity of species in liquid phase (solvents,ions, and dissolved organic molecules). However, the control of gasmolecule transport at gas-liquid interfaces remains largely unexplored,mainly due to the smaller sizes and greater diffusivities of both freeand dissolved gas molecules, as well as the spontaneous interfacial masstransfer to establish the corresponding equilibrium state. Nevertheless,the capability of dynamically modulating the transport behavior atgas-liquid interface is important for a wide spectrum of emergingenergy, biomedical, and chemical engineering applications, includingfluidic control in miniaturized devices, gas-involved chemicalreactions, controlled gas exchange, directional gas pumping, etc.

Nearly all the reported micro/nanoscale gas gating mechanisms areconfined to the field of microelectromechanical systems (MEMS), whichusually involve mechanical moving parts coupled to magnetic, electric,pneumatic, or thermal actuation methods. However, such designs ofteninevitably introduce dead volume to the system and are challenging torealize while maintaining low leakage rates, which can severelycompromise the effectiveness of gas gating. Moreover, MEMS-based gasvalves may also suffer from laborious and expensive fabrication,mechanical instability, and high energy consumption, hindering theircompatibility with large-scale applications. On the other hand,membrane-based systems for controllable gas transport have only beendemonstrated very recently using liquid-infused microporous membranes,where gases can only permeate through the membrane by deforming thepore-filling gating liquid above a specific pressure threshold. Despitebeing a breakthrough, the liquid-infused membranes are only capable ofbinary switching (open/closed) instead of continuous permeabilityadjustment, and the switching requires an appreciable pressure trigger.

Therefore, the development of smart gating membranes with dynamic andreversible control over gas transport behavior is still very much in itsinfancy, making research effort along this direction critically needed.

Herein, a new strategy was used to continuously and dynamically modulategas transfer at a gas-liquid interface, based upon reversibleelectrochemical metal deposition/dissolution (zinc, Zn) on conductiveporous membranes.

The high-porosity, low-tortuosity membrane ensured rapid gas transportat gas-electrolyte interface at open state (FIG. 5A). In the schematicillustration of FIG. 5A, the gating membrane is shown in its open state,where the anodic aluminum oxide membrane with ordered one-directionalpores allows for rapid mass transfer at the gas-liquid interface. Thetop surface of the membrane was rendered electrically conductive viaphysical deposition of a gold thin film. Through detailed study on therelationship between electrolyte formulation and the electrochemicalnucleation behavior, highly reversible cycling of metallic Zn (>99%Coulombic efficiency) was realized with excellent kinetics. As a result,a compact and uniform layer of Zn nanocrystals was formed on themembrane with minimum deposition capacity, affording an effective gasbarrier within at most a few minutes (FIG. 5B). In the schematicillustration of FIG. 5B, the gating membrane is shown in its closedstate. Electrodeposition of a dense metallic nanocrystal layer on theconductive membrane surface afforded an effective gas barrier to reducethe membrane permeability. By simply adjusting the amount ofelectrodeposited metal, a continuous-state tuning on gas permeabilitywas achieved, with values spanning over two orders of magnitude.Moreover, this electrochemically-mediated gas gating approach neitherinvolved mechanical moving parts nor introduced any dead volume whenswitching between open and closed states. Such configurationaladvantages are particularly desirable in processes such asmembrane-based gas absorption, which can offer higher efficiency andeasier operation compared to conventional dispersive gas-liquidcontactors via obviating the energy-consuming blown-down step betweencapture and release caused by headspace gas.

To highlight the versatility of the gating approach, a high-efficiencyelectrochemical carbon dioxide (CO₂) concentrator was demonstrated bysandwiching a redox-active CO₂ sorbent electrode between two gatingmembranes, with the two electrochemical circuits (gating and CO₂capture/release) sharing the same electrolyte. FIGS. 5C-5D show theoperational modes of the electrochemically-mediated CO₂ concentrator,which is constructed by integrating an electrochemical CO₂ capture cellwith two gating membranes. In this setup, Zn shuttling between thegating membranes opened one gate while simultaneously closing the other;and quinone-based CO₂ carriers, which were immobilized on a conductiveporous substrate, were able to reversibly bind/release CO₂ atreduced/oxidized form, respectively. The quinone molecules serve asredox-active sorbents for CO₂ capture and release, which can form stableCO₂ adducts when being reduced and release CO₂ when being oxidized.During capture, the system opened toward a dilute feed stream tocontinuously absorb CO₂ by the reduced sorbent, with the product-sidegate closed (FIG. 5C). Once the sorbent capacity was reached, the gatepolarity switched to close the feed-side gate and open the product-sidegate, releasing pure CO₂ into the product stream via electrochemicalsorbent oxidization (FIG. 5D). Thanks to the gating mechanism, thesystem could only access one gas stream at a time during operation,which greatly improved the separation efficiency by avoiding cross-talkbetween feed and product. As a result, the device can directionally pumplow-concentration CO₂ against a chemical potential gradient to nearpurity at atmospheric pressure using electricity as the sole drivingforce, with no upstream compressor or downstream vacuum needed.Integrating multiple such units operating at opposite polarities wouldallow for an effectively continuous CO₂ capture-release process, whichcan break new ground for niche gas separation applications.

Results and Discussion

Design Rationales of the Electrochemically-Mediated Gas Gating Membrane

A number of important design criteria were considered when designing theelectrochemically-mediated gas gating system.

First, a high-porosity membrane was desirable for rapid gas transport inan open state, yet it was desired to make the pore size small enough toreduce the amount of metal plating needed to achieve full pore blockage.Such material requirements made anodic aluminum oxide (AAO) an idealcandidate, which exhibits well-defined one-directional channels withhigh pore density, and a narrow pore size distribution of about 100 nmin this case (FIGS. 6A and 6C). A gold (Au) thin film (100 nm) wasthermally evaporated on one side of the AAO to render it electricallyconductive for gating metal deposition, as shown in the pictures, SEMimages, and energy-dispersive X-ray elemental mapping in FIGS. 6B, 6Dand 11A-11B. The AAO was peripherally bonded to an annular polypropylenesupporting ring for ease of handling.

Second, it was desired to select the gating metallic species such thatit would have satisfactory deposition/dissolution kinetics for a fastgating response. FIG. 12A is a diagram showing standard reductionpotentials of common metallic redox pairs; and FIG. 12B is a plot ofcurrent as a function of potential for 1.0 M Zn(NO₃)₂ in dimethylsulfoxide, 1.0 M Ni(NO₃)₂ in dimethyl sulfoxide, and 5 mM anthraquinonein dimethyl sulfoxide with 0.1 M tetrabutylammonium hexafluorophosphatesupporting salt under CO₂ atmosphere. Redox couples such as Li⁺/Li⁰,Na⁺/Na⁰, Mg²⁺/Mg⁰, and Zn²⁺/Zn⁰ generally fall into the category ofredox couples that have satisfactory deposition/dissolution kinetics fora fast gating response. However, metallic Li, Na and Mg are oftenplagued with high (electro)chemical reactivity due to their low redoxpotentials (FIG. 12A), making them difficult for use with many practicalgaseous environments. Also, Ni²⁺/Ni⁰ generally showed poorelectrochemical kinetics, as manifested from the large potentialdifference between plating and stripping. On the other hand, Zn isuniquely positioned for gas gating applications with advantageousfeatures of good air stability, low cost, and environmental benignity.

Generally, when the gating membrane is coupled with anotherelectrochemical process (for species capture) sharing the sameelectrolyte, the redox potential of the other electrochemical process(e.g., species capture) should be more positive than Zn²⁺/Zn⁰ to avoidbeing interfered with by the presence of Zn²⁺ in the electrolyte. Thiswas true for the quinone-based CO₂ capture/release process demonstratedin this study, as can be seen from the cyclic voltammetry (CV) in FIG.6E. In this study, 1.0 M Zn(NO₃)₂ in dimethyl sulfoxide and 5 mManthraquinone in dimethyl sulfoxide with 0.1 M tetrabutylammoniumhexafluorophosphate supporting salt were tested under CO₂ atmosphere.Glassy carbon (Ø3 mm) was used as the working electrode, Pt wire wasused as the counter electrode, Ag wire was used as a pseudo-referenceelectrode, and 1 mM ferrocene (Fc) was used as an internal reference.The scan rate was 50 mV/s. The inset of FIG. 6E shows the reversiblereaction between anthraquinone and CO₂. This study showed that the Zndeposition potential was appreciably lower than the reduction potentialof anthraquinone under a CO₂ atmosphere. In fact, the redox potential ofZn²⁺/Zn⁰ falls more negative than most practically-relevant gas-involvedelectrochemical processes, such as electrochemically-mediated gascapture and organic electrosynthesis, rendering this gas gating membranemechanism widely applicable.

Third, homogeneous electrodeposition with high reversibility is anotherdesirable property for effective gas gating. Aqueous Zn chemistrycommonly employed in battery research unfortunately suffers from lowefficiency (<50% in typical alkaline solution) and dendritic depositionmorphology, since metallic Zn is thermodynamically unstable in water.Therefore, a non-aqueous electrolyte was selected for use, which hasrarely been studied in literature.

In this study, propylene carbonate (PC) was selected as the electrolytesolvent due to its wide electrochemical stability window and low vaporpressure. The Zn plating morphology was first studied on Au-coatedaluminum foil (Au film was 100 nm thick) using 0.5 M zincbis(trifluoromethanesulfonyl)imide (ZnTFSI) in PC. The deposition wascarried out at a current density of 2 mA cm⁻² for 30 min. However, asseen from the scanning electron microscopy (SEM) images, Zn grew intolarge aggregates that only sparsely covered the substrate (FIGS.13A-13C), which stood in stark contrast to the continuous thin filmobtained in aqueous electrolyte, as shown in FIG. 14 , where pristinecopper foil is shown on the left, and the copper foil after Zndeposition using aqueous electrolyte is shown on the right. Thedeposition was carried out in 1.0 M aqueous solution of ZnSO₄ at acurrent density of 2 mA cm⁻² for 15 min. Such highly localizeddeposition behavior might be attributed to the relatively largeinterfacial energy between metallic Zn and PC. According to theclassical nucleation theory, the Gibbs energy for nucleation is the sumof the bulk and the surface free energy. High interfacial energy wouldtherefore result in low nucleation density and aggregated depositionmorphology to minimize the surface area. This hypothesis wascorroborated by the large nucleation overpotential observed for Zndeposition in PC electrolyte, which is defined as the magnitude of thevoltage spike at the onset of galvanostatic deposition (FIG. 6F). It wasfound that ethylene glycol (EG) could be employed as an electrolyteadditive to effectively reduce the interfacial energy. In this study, Znwas deposited on Au-coated aluminum foil in 0.5 M ZnTFSI PC electrolytewith different amounts of EG additive. The deposition was carried out ata current density of 0.5 mA cm⁻², and slurry-coated Zn powder was usedas the counter electrode to minimize the polarization contribution fromthe counter electrode. For better visual comparison, the profiles wereshifted vertically. The inset of FIG. 6F shows the photo image ofdeposition without EG and with 10% EG as additive. This study showedthat the nucleation overpotential decreased continuously with increasingamount of EG, and the addition of merely 10 vol % EG resulted in theformation of a highly uniform Zn film (FIG. 6F).

FIGS. 6G-6H show top-view SEM images of Zn deposits on an AAO membraneobtained in a 0.5 M ZnTFSI PC electrolyte with 10% EG additive at a highcurrent density of 3 mA cm⁻² for 10 minutes. A compact Zn filmconsisting of uniform, crystalline Zn polyhedrons was observed, and thehomogeneity persisted over the whole deposition area (FIGS. 15A-15B).Side-view SEM images and the corresponding energy-dispersive X-rayelemental mappings of Zn deposition on Au-coated AAO membrane indicateda tight coverage of Zn film on the surface of AAO (FIG. 6I and FIGS.16A-16E). The thickness of the film at a deposition capacity of 0.5 mAhcm⁻² was around 650 nm, which agreed exceptionally well with thetheoretical value of a dense Zn layer (655 nm). Such depositionmorphology was highly desirable for effective gas gating. The Zn cyclingCoulombic efficiency (CE), which is defined as the ratio betweendissolution and deposition capacity, is also important for reversiblegas gating. Unprecedented CE can be achieved using this PC-basedelectrolyte, with the value measured to be 99.3% at a high cyclingcurrent of 3 mA cm⁻² (FIGS. 17A-17B). The slightly reduced CE at evenhigher currents was mainly attributed to the early hitting of thecut-off potential rather than side reactions. Therefore, a low-currentdissolution step following extremely high-current cycling (12 mA cm⁻²)still effectively recovered >99% of the deposited Zn, which indicatedthat Zn cycling in the electrolyte system was mainly limited bykinetics, not side reactions (FIGS. 17A-17B). The depositions werecarried out in 0.5 M ZnTFSI PC electrolyte with 10% EG additive at acapacity of 0.5 mAh cm⁻².

Ex Situ Testing of the Electrochemically-Mediated Gating Membrane

One advantage of the electrochemically-mediated gating mechanism is itsability to modulate the membrane permeability continuously. A denser Znfilm and more complete pore coverage was observed on an AAO membranewith increasing deposition capacity, which in turn resulted indecreasing permeability (FIGS. 18A-18F). To verify the capability ofcontinuous-state tuning, membranes with different amount of Zn depositedwere first evaluated ex situ in both liquid and gas phase.

Liquid-phase diffusion experiments were conducted in an H-cellconfiguration using methyl orange dye as a tracker. 1 mM methyl orangeand pure water were separated by the membranes, and aliquots were takenfrom the permeate chamber to determine the cross-over concentration viaUV-vis spectroscopy (FIGS. 19A-19B). The corresponding calibration curveshown in FIG. 19B was based on the absorbance at 464 nm.

FIG. 7A is a set of photo images showing the liquid-state diffusiontests at different time points for pristine AAO and 0.5 mAh cm⁻² Zngated AAO, and FIG. 7B shows the cross-over dye concentration in thepermeate chamber as a function of time for pristine AAO, and AAO gatedwith 0.1, 0.3, and 0.5 mAh cm⁻² Zn. FIG. 7C is a schematic illustratingthe setup for ex situ gas-phase testing of theelectrochemically-mediated gating membrane. Membranes with differentamount of Zn deposited were mounted on brass gaskets, and theconcentration of CO₂ permeated through the membranes was determinedusing in-line CO₂ detector.

As can be clearly seen from FIG. 7A and FIG. 20 , the dye rapidlydiffused through the membrane at open state (pristine AAO), while thecross-over rate decreased gradually with increasing Zn capacity untilcolor change was barely visible over 24 hours for 0.5 mAh cm⁻² Zn gatedmembrane. Quantitatively, the cross-over concentration after 24 hourswas 297 μM for pristine AAO, but was 28.7, 5.6, and 1.1 μM for 0.1, 0.3and 0.5 mAh cm⁻² Zn gated AAO, respectively (FIG. 7B). Thus, even a lowdeposition capacity of 0.1 mAh cm⁻² (2 min deposition at 3 mA cm⁻²current) could already slow down the dye molecule diffusion by an orderof magnitude, and 0.5 mAh cm⁻² Zn effectively afforded a 300× reductionin membrane permeability.

Gas-phase gating, which is more demanding on the compactness of thegating metal layer, was also studied ex situ using CO₂ permeation as anexample. In this experimental setup, 15% CO₂ (balance N₂) was passed viaa mass flow controller (MFC) over one side of the membrane, whichcontained different amounts of deposited Zn, and the permeated CO₂ wasswept by pure N₂ towards an in-line gas analyzer to accurately determinethe concentrations (FIG. 7C). Detailed configuration of the gas cell isprovided as FIGS. 21A-21C. FIG. 21A shows the configuration of the gascell device used in all of the gas-phase experiments in this study. Theexact setup of the active membrane components differed in differentexperiments, with information given separately. The brass sample holderdisc for gating membrane mounting is shown in the schematic. FIG. 21Bshows the dimensions of the gas flow chamber, and FIG. 21C an image ofthe gas cell device. The permeation flux for all membranes increasedwith increasing flow rate difference between CO₂ feed stream and N₂sweep stream, which corresponded to a higher transmembrane pressure(FIG. 7D and FIGS. 22A-22B). In these ex situ experiments, the gas flowconditions were tested for pristine AAO, and AAO gated with 0.1, 0.3,and 0.5 mAh cm⁻² Zn. FIG. 22A shows the testing when the 15% CO₂ feedstream and N₂ sweep stream were under the same flow rates, and FIG. 22Bshows the testing when they were under different flow rates. The flowrates of the 15% CO₂ (balance N₂) feed stream and the N₂ sweep streamare indicated in the plot in FIG. 7D (sccm=standard cubic centimetersper minute). Consistent with liquid-phase experiments, the gaspermeability of the membrane also decreased continuously with increasingZn capacity under all the flow conditions tested. No CO₂ permeation wasdetected for 0.5 mAh cm⁻² Zn gated AAO unless subjected to an extremetransmembrane pressure (200 sccm feed and 5 sccm sweep), which alsotranslated into a two orders of magnitude reduction in gas permeabilitycompared to open-state membrane.

The success of the above ex situ experiments in both liquid and gasphase strongly demonstrated the effectiveness and wide tunability ofthis electrochemically-mediated gating membrane.

In Situ Testing of the Electrochemically-Mediated Gas Gating Membrane

In situ testing of the electrochemically-mediated gating membrane wasconducted to further verify its ability to reversibility and dynamicallycontrol gas transport at the gas-liquid interface. FIG. 8A is aschematic illustrating the setup. The setup was similar to ex situtesting, but the membrane was coupled with a mesh counter electrode withpre-deposited Zn (FIG. 8A and FIG. 23 ). In this setup, the mesh counterelectrode was selected because it had little impedance to gas flow. Zndeposition was carried out at a current density of 0.5 mA cm⁻² for 10hours using 0.5 M ZnSO₄ in EG as the electrolyte. The testing employed a“zero-gap” design, where the electrodes were in close contact with theelectrolyte-imbibed separator with no air gap in between. At open state,CO₂ was transported through the electrolyte-imbibed separator viadissolution-diffusion and outgas into the sweep stream.

FIG. 8B shows the sweep stream CO₂ concentration in response toreversible gating (10 min deposition/dissolution at 3 mA cm⁻², with 10min rest in between), where consistent gate open and close behavior wasobserved over 20 cycles. Looking at an individual cycle, the permeatedCO₂ concentration kept decreasing with increasing Zn deposition untilfinally no cross-over can be detected, followed by a gradual restore tothe open-state value with Zn dissolution (FIG. 8C). The discrepancybetween the onset of deposition/dissolution and the CO₂ signal responsewas believed to have been due to system dispersion and headspace volumeof the flow chamber. FIG. 24A shows the steady-state CO₂ cross-overconcentration using 10 sccm 100% CO₂ feed stream and 2 sccm N₂ sweepstream. Since the testing employed a zero-gap design, meaning that theelectrodes were in close contact with the electrolyte-imbibed separatorwith no air gap in between, CO₂ cross-over can only occur viadissolution-diffusion through the electrolyte. Therefore, the cross-overconcentration was much lower compared to the values in ex situ gas-phaseexperiments. FIG. 24B shows the characterization on the detectorresponse time. At time zero, 1% CO₂ was supplied through the inlet ofthe sweep stream at a flow rate of 2 sccm, and the detector showed CO₂response starting from 206 seconds. This lag time is due to flowdispersion of the gas testing device, as well as the headspace volume(flow chamber and tubing to detector). The lag time can consistentlyexplain the response of the gating membrane during in situ switching,where CO₂ permeation started to decrease ˜130 seconds after the onset ofZn deposition, and the CO₂ reading only reached 0 ppm ˜5 minutes aftercomplete deposition (FIG. 8C). Moreover, the in situ Zn cyclingdemonstrated an outstanding CE (averaged>99.5%, FIG. 8D) and stablevoltage profiles at 1^(st), 10^(th), and 20^(th) cycle during in situgas cell testing (FIG. 25 ), and both were strong evidence of the highreversibility of the gating membrane. Importantly, the gating kineticswere easily tuned by varying the cycling current, while stillmaintaining a remarkable gating on/off ratio (FIG. 8E). In thesestudies, the deposition capacity was kept constant (0.5 mAh cm⁻²).

Electrochemical Properties of the Redox-Active Quinone-Based CO₂ Sorbent

The development of high-efficiency CO₂ separation technologies iscrucial to greenhouse gas mitigation, petroleum, chemical, and heavyindustries, as well as specialty applications such as life support inconfined spaces. One emerging strategy involves electrochemical cyclesto capture/release CO₂, with quinones being a representative example.Electrochemically-reduced quinones can bind to electrophilic CO₂ to formstable adducts, while the oxidation of the adducts regenerates thesorbents to release CO₂. As a proof-of-concept, a quinone-based CO₂concentrator was demonstrated herein, where the utilization of gasgating membranes could prevent the undesirable cross-talk between thedilute and the concentrated gas streams, and in turn, significantlyimprove the separation efficiency.

A poly(1,4-anthraquinone) (PAQ)-carbon nanotube (CNT) composite wasselected as the electrode, due to its reduced solubility compared to themolecular counterpart (theoretical capacity=260 mAh g⁻¹, or 9.7 mmol CO₂g⁻¹). To facilitate liquid-phase CO₂ mass transfer, PAQ was casted on aporous carbon felt 50 μm in thickness and paired with LiFePO₄ (LFP)counter electrode (the PAQ-LFP electrode pair is termed the “CO₂ cell”hereafter). The electrolyte was 0.1 M LiTFSI+0.5 M ZnTFSI in PC with 10%EG. As seen from the capture-release voltage profiles, polarizationincreased with increasing PAQ mass loading and/or cycling rates,together with decreased capacity utilization (FIG. 9A). Therefore, 0.75mg cm⁻² loading with 30-min capture/release (0.4 mA cm⁻² current) wasidentified as an optimal cycling condition, under which satisfactorycarbon capture capacity was achieved while preserving goodelectrochemical kinetics and stability (FIG. 9B). In this study, eachcapture/release step was 30 min following a constant current(CC)-constant voltage (CV) protocol. The inset of FIG. 9B shows the SEMimage of the PAQ electrode.

To prevent this system from operating beyond the mass transfer limit,the limiting current density of the CO₂ cell was estimated based on thediffusion model described in FIG. 9C (See Supplementary Method 1 below).The limiting current is defined as the current when steady-state CO₂concentration reaches zero at the depth of the PAQ electrode. 15% CO₂was used in the calculation, which is the approximate concentrationexpected in most carbon capture applications. The limiting currentdecreased with decreasing gas pressure and/or increasing electrodethickness, with the value being ˜2 mA cm⁻² when using a 50 μm electrodeunder 1 atm pressure (FIG. 9D). Thus, the identified PAQ cyclingcondition did not exceed the limiting current, yet was close enough totake sufficient advantage of kinetics. The gap between the two alsoallowed a smaller gas-liquid contact area than the size of the CO₂ cell,which can reduce gating energy consumption.

When the CO₂ cell was tested by flowing CO₂ at one side and N₂ at theother, a cyclic fluctuation of the permeated CO₂ concentration wasobserved. FIG. 9E shows the CO₂ permeation in response toelectrochemical cycling of the CO₂ cell, and the corresponding voltageprofiles. In this study, the same device as gating membrane testing wasused. 1 atm 100% CO₂ was flowing on one side of the CO₂ cell and 1 atm 5sccm N₂ was flowing on the other, carrying permeated CO₂ to thedetector. FIG. 9F shows the detailed CO₂ permeation behavior during onecapture-release cycle marked with a dashed line in FIG. 9E. Duringcapture, CO₂ in the electrolyte was being actively consumed, resultingin a reduction in permeation When the cell reached the cut-off voltagefor CC capture, CV capture started with decaying capture rate, resultingin a gradual restore in CO₂ permeation. The subsequent CC releasegenerated CO₂ at a constant rate, leading to a sharp concentration spikeand the release rate decayed during CV release until permeation returnedto its background value (˜4500 ppm) (FIG. 9F). This behavior wasverified through a COMSOL transport model simulation, where thesimulation predictions match closely with the experimental results.

Nevertheless, a significant CO₂ permeation background existed (4500 ppmfor the cycle shown in FIG. 9F) when the cell was operated without thegating mechanism, due to spontaneous CO₂ diffusion down theconcentration gradient. In real separation scenario, since the cell hasaccess to both the dilute feed stream and the concentrated productstream, CO₂ would have a much higher tendency to be released back intothe feed unless enough differential pressure were created across thecell, which could severely compromise the separation efficiency.

High-Efficiency Electrochemical CO₂ Separation Enabled by Gas GatingMembranes

Integrating the CO₂ cell with this electrochemically-mediated gas gatingmembranes offers an exciting opportunity to overcome the abovementionedbarrier in separation efficiency. By sandwiching the CO₂ cell betweentwo gating membranes at opposite on/off states (termed the “gating cell”hereafter), the system can only access one gas stream at a time tocircumvent undesirable cross-talks caused by chemical potentialdifference.

FIG. 10A is a cross-sectional schematic illustrating the configurationof the integrated CO₂ separation system and detailed information isprovided as FIG. 26A-26E. The following design aspects were noted forhigh separation efficiency. (1) A “zero-gap” design was used where theCO₂ cell and the gating cell were in tight contact without headspace orgas bubbles to avoid gas-channeling. FIG. 26A shows the gating membraneswith a 1 cm² circular active area were mounted on brass gaskets. PAQ andLFP electrodes (1″×1″) were sandwiched between the gating membranes. Thecomponents were separated by electrolyte-imbibed polypropyleneseparators and confined with rubber gaskets without headspace gas. Theconductive side of the gating membrane faced the CO₂ cell. FIG. 26B is aphoto image of the gating membrane mounted on a brass gasket using epoxyglue. FIGS. 26C-26D show photo images of the LFP and PAQ electrode,respectively. FIG. 26E is a photo image of the rubber gasket used toconfine the CO₂ cell between the gating cell. (2) Minimum electrolytewas added such that the capture capacity of the CO₂ cell dominated overthe physical CO₂ solubility of the electrolyte (See Supplementary Method2 below). (3) The gating cell area (1 cm²) was smaller than the CO₂ cell(6.45 cm²) based on limiting current estimation to reduce gating energyconsumption. (4) The thickness of all components was reduced wheneverpossible to facilitate mass transfer. In real operation, the deviceworks by directionally pumping dilute CO₂ into a concentrated product.However, due to the limitation of this detection method, a N₂ sweep wasused in place of the product stream in order to monitor CO₂capture/release with a gas sensor. In this example, the gating cell isdescribed as being “closed” when the system is facing the feed stream tocapture CO₂, and as “open” when the system is facing the N₂ sweep streamto release CO₂ (FIG. 10B). Thus, under this testing condition, metricsdefining high efficiency separation included no CO₂ cross-over with gateclosed and a high concentration spike during CO₂ release at open gate.

FIG. 10C shows the CO₂ permeation during the operation of the integratedCO₂ separation system, and the corresponding voltage profiles of the CO₂cell and the gating cell. 1 atm 100% CO₂ was used as the feed streamfirst to maximize the measurement sensitivity, while 1 atm 2 sccm N₂ wasused as the sweep stream. Indeed, no cross-over was detected when thegate was closed, confirming that the system was only accessing the feedstream during electrochemical CO₂ capture. For each capture-releasecycle, the system started with a closed gate and the CO₂ cell waselectrochemically reduced to capture CO₂ from the feed stream (30 minCC-CV capture). After the capture capacity was reached, the gating cellswitched polarity and the gate was opened by shuttling Zn to the otherside of the gating cell (Zn cycling at 3 mA cm⁻² for 10 min), duringwhich a gradual permeation increase appeared due to CO₂ outgassing fromthe electrolyte. The permeation increased first followed by a gradualdecrease, since CO₂ in the electrolyte cannot be replenished from thefeed side. Subsequently, a distinct concentration spike was observedwhen the CO₂ cell was electrochemically oxidized to release the capturedCO₂ from the quinones. As the captured CO₂ was released from the CO₂cell, it resulted in a pronounced concentration spike (30 min CC-CVrelease). Finally, the CO₂ signal decayed back to zero by switching thegating cell polarity to close the gate, thus completing acapture-release cycle (Zn cycling at 3 mA cm⁻² for 10 min). Consistentbehavior was observed over multiple cycles (FIGS. 27A-27C). FIG. 27Ashows a typical voltage profile of the gating cell in the integrated CO₂separation system, while FIG. 27B shows a typical voltage profile of theCO₂ cell in the integrated CO₂ separation system and FIG. 27C shows acontinuous capture-release cycling of the integrated CO₂ separationsystem with 100% CO₂ as the feed stream. After qualitatively comparingthe system efficiency by the ratio between the magnitude of theconcentration spike and the permeation background, the value was ˜0.39for the integrated system while it was only ˜0.19 without gatingmechanism. Moreover, by lowering the feed concentration to morepractical values (20% CO₂), transport to the product stream wasdominated by the contribution from the CO₂ cell, as shown in thecontinuous capture-release cycling of the integrated CO₂ separationsystem in FIG. 10D. The results fulfilled the abovementioned metrics forhigh-efficiency separation. These phenomena were also observed in thecorresponding COMSOL transport model simulation, which allow forprediction of system performance for different gas compositions andoperation parameters (FIG. 10D).

Therefore, the realization of reversible, dynamic transport control at agas-liquid interface uniquely enabled directional CO₂ pumping withoutthe need for differential pressure. Combining multiple units operatingat opposite polarities could afford an effectively continuous CO₂capture-release process. Compared to conventional batch processes, thismembrane-based “zero-gap” CO₂ separation device obviates the need forsystem blow-down between absorption and regeneration, which can simplifyreactor design and improve energy efficiency for industrial carboncapture. Moreover, this novel gas separation process could also openunprecedented opportunities for niche applications, such as life supportsystems in manned space/marine missions and electrochemical gascompression.

CONCLUSIONS

Controlling transport behavior at gas-liquid interface is a largelyunder-researched topic albeit being crucial for emerging technologies.In this work, a novel gating mechanism capable of dynamically andcontinuously modulating gas transport at gas-liquid interface, driven byelectrochemical metal deposition/dissolution on conductive porousmembrane in rationally-formulated electrolyte is proposed. The gasgating membrane can operate with excellent on/off ratio, reversibility,kinetics and tunability as verified by both ex situ and in situ testing.Moreover, actuated only by electrochemistry, the gating membrane neitherinvolves moving parts nor headspace, which are desirable for high gatingefficiency and reliability. As a proof-of-concept, anelectrochemically-mediated carbon dioxide concentrator was demonstratedby sandwiching a redox-active CO₂ sorbent electrode between two gatingmembranes. The gating mechanism effectively minimized cross-talksbetween feed and product streams, such that the integrated device coulddirectionally pump CO₂ against concentration gradient without the needfor differential pressure, making it versatile to diverse carbon captureapplications. This concept of dynamically regulating mass transfer atgas-liquid interface could inspire novel applications in wide fieldsranging from gas separations, miniaturized energy/medical devices tomicroscale gas-involved reactors and beyond.

Methods

Materials.

AO membranes were purchased from Whatman (Anodisc 6809-6012, 25 mmdiameter, 100 nm pore size), and were rendered electrically conductiveby depositing 100 nm Au on one side of the membrane via thermalevaporation. The electrolytes were prepared by dissolving thecorresponding salts zinc bis(trifluoromethanesulfonyl)imide (AlfaAesar), lithium bis(trifluoromethanesulfonyl)imide (Solvay), and/ortetrabutylammonium hexafluorophosphate (Sigma-Aldrich) in propylenecarbonate (anhydrous, 99.7%, Sigma-Aldrich), ethylene glycol (anhydrous,99.8%, Sigma-Aldrich) and/or dimethyl sulfoxide (Sigma-Aldrich).Propylene carbonate and ethylene glycol were dried over molecular sieves(4 Å, Sigma-Aldrich) before use. Ferrocene and anthraquinone werepurchased from Sigma-Aldrich.

Characterizations.

EM images and energy-dispersive X-ray elemental mappings were taken witha Zeiss SUPRA 55-VP scanning electron microscope. Liquid-phase diffusiontests were carried out in 5 ml H-cells (Adams & Chittenden ScientificGlass). The two chambers were separated by AAO membrane with 0.5 cm²effective area. Methyl orange concentration in liquid-phase diffusiontest was determined using a UV-vis spectrometer (Ocean Optics).

Electrochemical Zn Cycling.

Electrochemical measurements were conducted using a VersaSTAT4potentiostat (Princeton Applied Research). To study the Zn depositionmorphology, either Au-coated AAO or Au-coated aluminum foil was used asthe substrate. The deposition was carried out in a pouch cellconfiguration with glass fiber separator (MilliporeSigma) and Zn foil(0.25 mm thick, Fisher Scientific) counter electrode. Zn foil waspolished progressively down to 7000 grit sandpaper before use. For thestudy of nucleation overpotential, Zn dust (<10 μm, Sigma-Aldrich)counter electrode was used, which was fabricated by mixing 80% Zn dust,10% carbon black (Super P, MTI Corp.) and 10% polyvinylidene fluoride(Sigma-Aldrich) in N-methylpyrrolidinone followed by slurry coating onaluminum foil.

Ex Situ and In Situ Gas Cell Measurements.

The gas-phase measurements were conducted using a house-machined deviceconsisting of two gas flow chambers separated by the gating membrane,all held together with rubber gaskets and screws (detailed gas cellconfiguration shown as FIG. 21A). Membranes were mounted on brass holderdiscs using 5-minute epoxy glue (Devcon). CO₂ of differentconcentrations flowed through one gas chamber and N₂ sweep gas flowedthrough the other. The concentration of CO₂ in the N₂ stream wasmeasured with an in-line CO₂ sensor (ExplorIR®-W 20% CO₂ sensor). Thesensor had a measurement range of 0-20% CO₂ and an accuracy of ±70 ppm.

For in situ testing of the gas gating membrane, the membrane was coupledwith a stainless-steel mesh (316 stainless-steel, 100 mesh,McMaster-Carr) counter electrode with pre-deposited Zn, and the twoelectrodes were separated by glass fiber separator.

Testing of the CO₂ Cell.

To obtain the PAQ-CNT composite, PAQ was dissolved in chloroform (1 mgmL⁻¹) using probe sonicator (Cole-Parmer Ultrasonic Processor, pulsermode: on 5 s—off 3 s, 60% amplitude). Subsequently, CNT was added intothe solution (1 mg mL⁻¹) and the mixture was sonicated for another 20min to afford a homogeneous dispersion. The PAQ-CNT ink was thendrop-casted on 50 μm carbon felt (Fibre Glast Carbon Fiber Veil). TheLFP counter electrode was prepared by mixing 95% LFP (MTI Corp.), 2.5%carbon black and 2.5% polyvinylidene fluoride in N-methylpyrrolidinonefollowed by drop-casting on 50 μm carbon felt (mass loading 8 mg cm⁻²).The PAQ electrode and the LFP electrode were separated with a 25 μmpolypropylene separator (Celgard 3501). The electrochemical cycling ofthe CO₂ cell was carried out using constant current followed by constantvoltage until the current decays to 20% the value of the constantcurrent cycling. The electrolyte used was 0.1 M LiTFSI+0.5 M ZnTFSI inPC with 10% EG additive.

Testing of the Integrated CO₂ Separation System.

Zn was pre-deposited on one of the AAO membranes (0.6 mAh cm⁻², 0.5 mAhcm⁻² Zn cycling capacity plus 20% extra to compensate Coulombic loss).The size of the PAQ electrode was 1″ by 1″ with an active material massloading of 0.75 mg cm⁻². The size of the LFP electrode was 1″ by 1″ withan active material mass loading of 8 mg cm⁻². The AAO membranes and theelectrodes were separated with 25 μm polypropylene separators andconfined tightly using gaskets. CO₂ (100% or 20%) was used as the feedstream and N₂ was used as a sweep stream for detection purpose. Acomplete capture and release cycle started with 30 min of CC-CV CO₂capture with gate closed. Once the capture capacity was reached, thepolarity of the gating cell was switched at 3 mA cm⁻² for 10 min,followed by 5 min rest. Subsequently, CO₂ was released from the PAQelectrode by 30 min of CC-CV oxidation, followed by 10 min rest.Finally, the cycle was completed by switching the polarity of the gatingcell again (3 mA cm⁻² for 10 min).

Supplementary Method 1.

Limiting current density determination of the PAQ electrode. A 1-D modelwas implemented to simulate the limiting current density of the PAQelectrode, defined as the current density when the steady-state CO₂concentration reaches zero at the depth of the electrode.

The following geometry was defined:

-   -   Thickness of the gas boundary layer=1 μm,    -   Thickness of a stagnant electrolyte layer=25 μm.

The following parameters were used:

-   -   Gas-phase CO₂ diffusivity=0.2×10⁻⁴ m²/s,    -   Henry's law constant of CO₂ in PC solvent=80 atm,    -   CO₂ diffusivity in PC solvent=1.2×10⁻⁹ m²/s,    -   PAQ electrode porosity=0.5,    -   PAQ electrode tortuosity=2.        Supplementary Method 2.

Electrolyte CO₂ solubility vs the CO₂ cell capacity.

Separator porosity (Celgard 3501, 25 μm)=55%

PAQ and LFP electrode porosity (50 μm)=50%

Area of the CO₂ cell=6.45 cm²

Total pore volume=3×6.45 cm²×25 μm×55%+2×6.45 cm²×50 μm×50%˜60 μL

Henry's law constant of CO₂ in PC solvent=80 atm,

PC density=1.2 g cm⁻³

PC molecular weight=102.09 g mol⁻¹

PC molar concentration=1.2 g cm⁻³/102.09 g mol⁻¹˜11.75 M

CO₂ solubility in PC (100% CO₂, 1 atm)=1 atm/80 atm×11.75 M˜0.147 M

CO₂ dissolved in electrolyte (100% CO₂, 1 atm)=0.147 M×60 μL˜0.0088 mmolCO₂

Difference in dissolved CO₂ between 20% and 100% CO₂ at 1 atm=0.0088×80%mmol˜0.007 mmol CO₂

CO₂ capture capacity of PAQ under 2 C cycling condition ˜7.5 mmol g⁻¹

Total capacity of the PAQ electrode=0.75 mg cm⁻²×6.45 cm²×7.5 mmolg⁻¹=0.036 mmol CO₂

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,and/or methods, if such features, systems, articles, materials, and/ormethods are not mutually inconsistent, is included within the scope ofthe present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. A method, comprising: transporting a fluidthrough a first electronically conductive porous solid such that aspecies from the fluid is captured by a medium adjacent to the firstelectronically conductive porous solid; altering an electrical potentialapplied between the first electronically conductive porous solid and asecond electronically conductive porous solid such that the fluidpermeability of the first electronically conductive porous solid isreduced and the fluid permeability of the second electronicallyconductive porous solid is increased; and releasing the species from themedium such that the species is transported through the secondelectronically conductive porous solid.
 2. The method of claim 1,wherein the fluid comprises a gas.
 3. The method of claim 1, wherein thespecies comprises an acid gas and/or a hydrocarbon gas.
 4. The method ofclaim 1, wherein at least one of the first electronically conductiveporous solid and the second electronically conductive porous solidcomprises a metal.
 5. The method of claim 4, wherein the metal is coatedon an electronically insulating porous solid.
 6. The method of claim 1,wherein altering the electrical potential applied between the firstelectronically conductive porous solid and the second electronicallyconductive porous solid such that the fluid permeability of the firstelectronically conductive porous solid is reduced comprises altering theelectrical potential such that a material is deposited over pores of thefirst electronically conductive porous solid.
 7. The method of claim 6,wherein the material deposited over pores of the first electronicallyconductive porous solid comprises a metal and/or a metal oxide.
 8. Themethod of claim 6, wherein the deposition of material over pores of thefirst electronically conductive porous solid comprises deposition ofcolloidal particles over pores of the first electronically conductiveporous solid.
 9. The method of claim 6, wherein the deposition ofmaterial over pores of the first electronically conductive porous solidcomprises precipitation of the material over pores of the firstelectronically conductive porous solid.
 10. The method of claim 1,wherein altering the electrical potential applied between the firstelectronically conductive porous solid and a second electronicallyconductive porous solid such that the fluid permeability of the secondelectronically conductive porous solid is increased comprises alteringthe electrical potential such that material is removed from pores of thesecond electronically conductive porous solid.
 11. The method of claim1, wherein the medium comprises a sequestration material.
 12. The methodof claim 11, wherein the sequestration material captures the species viaa non-electrochemical mechanism.
 13. The method of claim 12, wherein thenon-electrochemical mechanism comprises adsorption, absorption, and/or anon-electrochemical chemical reaction.
 14. The method of claim 11,wherein releasing the species from the medium comprises exposing themedium to a stimulus.
 15. The method of claim 14, wherein the stimuluscomprises a change in temperature and/or a change in pressure.
 16. Themethod of claim 11, wherein the sequestration material comprises azeolite, a metal-organic framework, a resin, and/or an electrolyte. 17.The method of claim 1, wherein the medium comprises a first electrodeand a second electrode.
 18. The method of claim 17, further comprisingapplying a first medium electrical potential between the first electrodeand the second electrode of the medium such that the species from thefluid is electrochemically captured by the medium.
 19. The method ofclaim 18, further comprising applying a second medium electricalpotential between the first electrode and the second electrode of themedium, the second medium electrical potential having a polarity that isthe opposite of the polarity of the first medium electrical potential,such that the species captured by the medium is released by the medium.20. A device, comprising: a first electronically conductive poroussolid; a second electronically conductive porous solid electronicallycoupled to the first electronically conductive porous solid; and amedium between the first electronically conductive porous solid and thesecond electronically conductive porous solid; wherein the device isconfigured such that: when an electrical potential is applied to thefirst and second electronically conductive porous solids with a firstpolarity, a fluid permeability of the first electronically conductiveporous solid is reduced, and when an electrical potential is applied tothe first and second electronically conductive porous solids with asecond polarity opposite the first polarity, the fluid permeability ofthe second electronically conductive porous solid is reduced.
 21. Thedevice of claim 20, wherein the device is configured such that: when theelectrical potential is applied to the first and second electronicallyconductive porous solids with the first polarity, a fluid permeabilityof the second electronically conductive porous solid is increased, andwhen the electrical potential is applied to the first and secondelectronically conductive porous solids with the second polarityopposite the first polarity, the fluid permeability of the firstelectronically conductive porous solid is increased.
 22. The device ofclaim 20, wherein at least one of the first electronically conductiveporous solid and the second electronically conductive porous solidcomprises a metal.
 23. The device of claim 22, wherein the metal iscoated on an electronically insulating porous solid.
 24. The device ofclaim 20, wherein the device is configured such that when the electricalpotential is applied to the first and second electronically conductiveporous solids with the first polarity, a material is deposited at aninterface between the medium and the first electronically conductiveporous solid.
 25. The device of claim 24, wherein the material depositedat the interface between the medium and the first electronicallyconductive porous solid comprises a metal and/or a metal oxide.
 26. Thedevice of claim 24, wherein the material deposited at the interfacebetween the medium and the first electronically conductive porous solidcomprises a colloidal particle.
 27. The device of claim 20, wherein thedevice is configured such that when an electrical potential is appliedto the first and second electronically conductive porous solids in asecond polarity opposite the first polarity, material is deposited at aninterface between the medium and the second electronically conductiveporous solid.
 28. The device of claim 27, wherein the device isconfigured such that when the electrical potential is applied to thefirst and second electronically conductive porous solids in the secondpolarity opposite the first polarity, material is removed from aninterface between the medium and the first electronically conductiveporous solid.
 29. The device of claim 20, wherein the medium comprises asequestration material.
 30. The device of claim 29, wherein thesequestration material comprises a zeolite, a metal-organic framework, aresin, and/or an electrolyte.
 31. The device of claim 30, wherein themedium comprises a metal salt dissolved in a solvent.
 32. The device ofclaim 20, wherein the medium comprises a first electrode and a secondelectrode.
 33. The device of claim 32, wherein the medium is configuredsuch that when a medium electrical potential is applied between thefirst electrode and the second electrode of the medium, a species iscaptured by the medium.
 34. The device of claim 33, wherein the mediumis configured such that, when a second medium electrical potential isapplied between the first electrode and the second electrode of themedium, the second medium electrical potential having a polarity that isopposite the polarity of the first medium electrical potential appliedbetween the first electrode and the second electrode of the medium, thespecies is released by the medium.